Five years after Jemma Simmons and Leopold Fitz signed on to become Agents of S.H.I.E.L.D., the words "Will you marry me?" were spoken. Fittingly, they both asked each other (but it was Jemma's proposal that 'counts', as she couldn't hear Fitz when he asked). After all this time of being literally star-crossed, separated, reunited, but never wavering in their commitment to each other, fans of Marvel's Agents of S.H.I.E.L.D. have been promised the wedding that we - not to mention Jemma and Leo themselves - have long pined for. A wedding that will seal what we all know to be true: FitzSimmons is the greatest romance in the Marvel Cinematic Universe.Portrayed with unmatched chemistry by Elizabeth Henstridge and Iain De Caestecker, no one else in the decade-old MCU can compare to FitzSimmons. Marvel may be the very finest at delivering superhero blockbuster movies with characters fans have fallen in love with, but romance is not the MCU's forte, and never has been. This was evident right at the MCU's inception with the love affair between Tony Stark and Pepper Potts. Pepper was originally the long suffering personal assistant subservient to her boss Tony's whims, eccentricities, and sexual dalliances. Even when Tony declared his love for Pepper and promoted her to CEO of Stark Industries, they were hardly equals. Arguably the only one who really admires this pairing and desires a storybook ending with Pepper is Tony himself. And this is the foundational romance of the MCU.Related: Season 5 Successfully Soft Reboots Agents of S.H.I.E.L.D.Tony Stark Pepper Potts Iron ManThe rest of the Marvel movie pairings aren't any more inspiring, save perhaps for the fleeting and doomed World War II romance between Steve Rogers and Peggy Carter. Steve and Peggy simply didn't have enough time, with fate cruelly creating a situation where Steve remains young and vital while Peggy lived a heroic life for decades without him, aged, and died - though they briefly and sweetly reunited. As consolation, Steve has sparked a romance with Peggy's much, much younger niece Sharon Carter, but even they have been kept apart as a result of the Avengers' Civil War.In terms of the other major MCU romances, Thor and Jane Foster started off strong but went kaput. Fans really did not care for Joss Whedon's attempt to romantically pair Natasha Romanoff and Bruce Banner, nor is anyone particularly rooting for Dr. Christine Palmer to end up with Doctor Stephen Strange. The jury's out on Scott Lang and Hope Van Dyne, and Peter Quill doesn't seem to have much of a shot with Gamora, despite his childish efforts. For everything the Avengers and the Guardians of the Galaxy get right as superhero movies, those looking for a genuine love affair between these beloved characters must look elsewhere.The love stories found throughout Marvel Television aren't much better. Matt Murdock's relationships with Karen Page and Elektra Natchios are both disasters. The comic book marriage between Jessica Jones and Luke Cage hasn't materialized; Cage is romantically involved with Claire Temple, though this seems to be a relatively solid coupling. Fans are left bewildered by what exactly the capable and admirable Colleen Wing sees in Danny Rand. Meanwhile, within Agents of S.H.I.E.L.D., Phil Coulson and Melinda May's unspoken but deeply felt relationship has been simmering for years, while Daisy Johnson has been so unlucky in love, it's inhuman. At least, Mack McKenzie and Yo-Yo Rodriguez seem to be forging a real connection, though they're understandably taking it slow.Related: Agents of S.H.I.E.L.D. Wrote Ming-Na Wen's Injury Into The StoryIn regards to Marvel romance, FitzSimmons is the pinnacle - and deservedly so. It's safe to say they were literally made for each other. Even from the very beginning of the series, fans and the characters themselves were in immediate agreement: we all wanted to see FitzSimmons together. They were simply adorable together: both squeaky-clean young scientists from the UK launched into the world-saving adventures of S.H.I.E.L.D. That they started together as colleagues who shared not just a fondness but a mutual respect - she a biochemist with numerous Ph.D.s and he a genius engineer who created little robots and desired a pet helper monkey - only made their connection sweeter. They were a team within a team, two peas in a pod, so much so that Coulson coined the name and introduced them as "FitzSimmons". Even early on, they were one, but neither felt they were in a position to express and pursue the obvious.FitzSimmons was never a case of unrequited love, even from the start. This wasn't an unbalanced romance, of one pining for the other who was unaware or dismissive. They were mutually interested, but they were both inexperienced, so it was easy to place the work of fighting evil with S.H.I.E.L.D. first. But they were always equals. Even within their differing fields of expertise, they each acknowledged the other was the best at what they do, and they supported each other's ingeniousness- even pushing each other to reach new realms of brilliance. They were - and are - a team of the two best in their fields who inspire each other to be even better, especially better people.They have certainly suffered together. Their worldviews were shattered by HYDRA's subjugation of S.H.I.E.L.D. They were left to die at the bottom of the ocean by Grant Ward, with Simmons finding strength she never knew she had (something she would continually discover) to save Fitz. They've faced Inhumans, monsters both human and alien, and they've repeatedly been torn apart. Who can blame them for believing for so long that they've been cursed to never be together? Simmons was literally ripped from the Earth and banished to an alien world, where she fought for her very survival. For his part, Fitz never once considered abandoning Simmons or accepted that finding her and rescuing her was hopeless. Fitz spearheaded the all-out effort to cross the vastness of space itself to find Simmons and bring her home.Related: If Agents of S.H.I.E.L.D. Season 6 Happens, What Would It Be About?In the virtual reality of the Framework, which explored the darkest recesses of Fitz manifesting as one of the leaders of HYDRA, Simmons in turn simply would not accept this monster was the reality of the man she loved - and she was right. Even when the evil Fitz was romantically involved with Aida, Simmons dismissed it and saw the real Fitz throughout. Immediately after they destroyed the Framework, they were separated again - by time. With Simmons trapped with their friends 90 years in an apocalyptic future, Fitz rallied and found his best self. He dedicated every waking moment and all of his considerable brainpower to figuring out how to find Jemma. Fitz literally took "the long way" to Simmons, cryogenically freezing himself for decades before donning a guise as an intergalactic marauder to save her from slavery by the Kree. When they fought their way to safety, they fought together as a unit, and they saved their powerful superhero friend Quake in the process.Does it matter that when Fitz first proposed, Simmons didn't hear her because Kasius had robbed her of her hearing, so that it's Simmons' proposal that is the 'official' proposal? Well, maybe it does a little to Fitz, but in the end, he doesn't care. Because he recognizes the truly important thing: Jemma Simmons is the one for him, and she feels the same. They always felt the same about each other. Now, they're matured, as Agents of S.H.I.E.L.D., but more importantly, as two people who repeatedly overcome insurmountable odds, and they're ready to commit to each other forever.Related: Who Died On Agents of S.H.I.E.L.D. This Week?If Jemma Simmons and Leo Fitz are 'cursed', it turns out everyone should be so lucky to be as cursed as they are. Fitz and Simmons are, in a very real way, the beating heart and soul, not just of Agents of S.H.I.E.L.D. but of the entire MCU. They are goals for everyone to emulate, and despite all that the writers have done to test their romance, FitzSimmons endures as the shining example of perfect love in the MCU. Their road together has never been easy, and no doubt, they'll endure even more trials that will test them, up to and including their wedding day and beyond. But in a superhero universe known for the flaws and failings of its characters, FitzSimmons is a love affair that is continually inspirational and aspirational.When FitzSimmons' wedding day finally comes (we hope a tragedy isn't what has been teased will 'destroy fans'), there will be pints and there will be gin, and there will be a joyous celebration from their fans that, against all odds, those two crazy, brilliant kids made it.NEXT: AGENTS OF S.H.I.E.L.D. ANSWERED BIG SEASON 5 QUESTIONSMarvel's Agents of S.H.I.E.L.D. airs Fridays @ 9pm on ABC.