True to its name, The Flash quickly embedded itself as a cultural phenomenon almost immediately after it aired. Thanks to the show's ability to stick largely to its source material, fans keep on coming back to see the Scarlet Speedster face off against the many metahumans of Central City.
The show has also delivered more than its fair share of romance, with almost all the main characters falling in love at some point or another. Happily, a lot of these relationships were incredibly successful and continue to this day but there are others that simply haven't worked and so became tiring and annoying to watch.
Best - Cisco and Gypsy
Cisco hasn't really had much luck when it comes to love. He had a brief fling with Kendra that was over before it began and shared a mutual attraction with Leonard Snart's sister but ultimately that never went anywhere. The first time viewers saw Cisco in a committed, loving relationship was when he was with Gypsy.
Originally serving as a partial antagonist for Team Flash, Gypsy and Cisco were immediately attracted to each other. The biggest hurdle in their relationship was the fact that Gypsy was from a completely different Earth but thanks to Cisco's breaching ability, it was manageable. This couple had amazing chemistry and it was disappointing to see them end things.
Worst - Barry and Felicity
Before Olicity came along, these two adorable geeks looked like they were perfect for each other. Apart from the fact they both loved other people, obviously. When Barry first appeared in the Arrowverse by helping Oliver Queen with a case, there was no denying that there was a spark between him and Felicity.
However, in Season 1 of The Flash, it was made very clear from the start that Iris was Barry's true love. After only watching a couple of episodes, no one could deny that Barry and Iris were meant to be. Even Barry and Felicity recognized this when the latter came to visit Barry in Central City.
Best - Caitlin and Killer Frost
First things first: yes, these two are a couple. Period. The way their relationship has evolved over the last 5 seasons has been incredible (and admittedly, a little weird). It's easy to forget now but when Earth-1's Killer Frost made her debut, she was one of the strongest and most dangerous villains Team Flash had encountered at that point.
Thankfully, over time, she's chilled out (pun intended) and she and Caitlin started to get used to sharing the same body. The two even struck up an adorably cute friendship, each acting as the other's confidante.
Worst - Iris and Eddie
Yet another relationship that served as a blockade to a fan-favorite coupling, Iris and Eddie simply weren't meant to be. The problem was that they were actually quite good together. They trusted each other and cared deeply about their relationship.
However, their relationship also had the unfortunate effect of making the show's titular hero less likable. Barry is by no means perfect but the way he acted in Season 1 just made him look petty and jealous. He wouldn't really speak to Eddie because he thought he had some unspoken right to Iris. A good hero needs to be watchable so this couple just wasn't good for the series.
Best - Caitlin and Ronnie
Viewers were on board with this couple from the moment they first saw poor Ronnie 'die'. Caitlin and her fiancee had amazing chemistry and we really felt Caitlin's pain after he was gone, even more so after watching that tragic flashback sequence.
You can't keep a good thing down however, as Ronnie managed to survive the particle accelerator explosion and merged with Professor Stein to become Firestorm 1.0. This meant that he and Caitlin were able to briefly rekindle their relationship before Ronnie sacrificed himself permanently to save Central City.
Worst - Cisco and Kamilla
The newest couple on this list, Cisco and Kamilla just don't feel right. They're quite dull compared to all the other entries in this article. In the past, Cisco has had some incredibly interesting relationships, which either contributed to the overall storyline or made the audience want to see more of them.
Kamilla just doesn't add anything to Cisco, or Team Flash. We're not saying she's a badly written character, but more could be done to make her less two dimensional. Cisco suffers because of that. He took the metahuman cure, mostly to be with her which is cute and everything, but was it entirely necessary?
Best - Barry and Iris
Of course, these two are one of the best couples on The Flash. The series wouldn't be worth watching if they weren't. Barry and Iris were adorable together even before they became an item and they've gone on to become one of the most popular couples, not just on The Flash, but in the entire Arrowverse itself.
Naturally, the show has put these two through the proverbial wringer on more than one occasion. From future Iris's death to their daughter being wiped from existence, Barry and Iris have faced many tragedies. However, this is what makes them such a strong couple, and The Flash is better for it.
Worst - Wally and Jesse
Ugh. This couple didn't just lack chemistry, it lacked everything! There was no love or commitment or any grand gestures so the whole relationship could be summed up in just one word: meh. This was unfortunate because Wally was actually a great character and deserved so much better from his first relationship.
Jesse, on the other hand, was not so great. She was basically in the show to raise the stakes and bring character and warmth to the coldest Harrison Wells we've seen so far. Admittedly, it worked and Wells became a more sympathetic character but the way Jesse ended her relationship with Wally was beyond callous.
Best - Joe and Cecile
The parent figures to Barry, Iris and, let's face it, the rest of Team Flash, Joe and Cecile were attracted to each other from the moment they laid eyes on each other. They're both extremely morally sound and very strong-willed which does mean they disagree occasionally but they never disregard the other's opinion.
Cecile was also the first woman who Joe dated after Iris and Wally's mother died so it was a big deal for Joe to put his trust in another person romantically. Thankfully, Cecile never let him down and the two went on to become an amazing couple, complete with a newborn child.
Worst - Caitlin and Jay
When Caitlin and Jay got together, it was problematic for several different reasons. First of all, Caitlin's husband, Ronnie, had only just died in the previous season's finale so it felt weird to see Caitlin fall in love so soon after Ronnie's demise.
Secondly, and most importantly, Jay wasn't who he said he was. Jay was, in fact, the main antagonist of Season 2, Zoom himself. Obviously Caitlin didn't know this when she and Jay became a couple but considering that he went on to take Barry's speed and kill his father, she might have picked up on it sooner.