The four main characters in Seinfeld go from smart and kind-hearted to inane and obnoxious at the drop of a hat. In many ways, they are meant to encapsulate the entire range of human emotion of those who live in NYC, although they often take their behavior overboard on several occasions.
The problem with trying to analyze characters who carry such incredible complexity within their personas is that they tend to exhibit different features at different times. For instance, George becomes ridiculously intelligent when he abstains from intercourse, but his normal state is not impressive in the slightest. These paradoxes apply to the other three just as much.
Jerry's Best: He's The Only (Relatively) Balanced Member Of The Group
Jerry is quite at peace with his life — it's obvious that doing stand-up gives him a solid financial safety net. He has most of his affairs in order, and has no qualms lending his friends exorbitant amounts of money or even buying his parents a very expensive Cadillac (that he later repurchases after his father sells it off).
His apartment isn't a disaster, his dating life, though inconsequential, is consistent, and he is generally not perturbed by most minor problems like his friends are. Jerry is, according to Kramer, an "Even Steven."
Jerry's Worst: Doesn't Really Care About His Friends
On the other hand, Jerry's love for George, Kramer, and Elaine seems to be conditional on how much entertainment they provide him. He obtains enough comedy material from their endless antics, which is probably the only reason he hangs out with them in the first place.
Whenever his friends narrate their sob stories to him, Jerry doesn't respond much, unless it's with his classic (and super-sarcastic) catchphrase, "that's a shame."
Elaine's Best: Actually Has A Proper Career
Although Jerry's profession is a lot better paying than Elaine's, being a performing artist is not exactly a stable job. It has its ups and downs, something that a regular 9-to-5 office stint does have.
Elaine does rotate through different jobs, but this doesn't mean that she's terrible at them (like George), or that she gets bored quickly (like Kramer). The fact remains that she knows how to keep her career going, which is impressive for the simple reason that office jobs can be draining and devitalizing.
Elaine's Worst: Pretends To Be Progressive But Isn't
Elaine goes on and on about a number of social justice issues, from feminism to environmentalism and everything in between. She scolds people for eating tuna (because of "the dolphins"), but has no personal issues with parading around in a fur coat just to satisfy her sense of self-importance.
Elaine has also spoken at length about her view of dating, and that it has no bearing on her partner's appearance, that is until she dumps Tony after his face is injured in a rock-climbing mishap or when she dumps Kurt because he'll be bald in 10 to 14 months.
Kramer's Best: Extremely Friendly And Likable
Kramer makes friends everywhere he goes, and while some of them may not exist (Bob Sacamano), others are quite happy to share their lives and their problems with him. He can be truly considerate, on occasion, even if this generosity rarely extends towards Jerry.
Kramer's best feature, however, is that he is absolutely filter-less — he says the first thing that pops into his brain, no matter how indecorous it might sound to others. That said, he rarely receives blowback for his "brutal honesty" because the people he directs his observations at are impressed by how sincere he is.
Kramer's Worst: Creates Problems And Exhibits No Shame About Them
In many situations, it would be prudent not to depend on Kramer for a solution, because the man has his head so far in the clouds that everything else seems hazy to him.
He is known to cause disasters, like his accidental arson of the Ross' cabin, but the worst part is that he doesn't acknowledge his role in the matter (let alone feel guilty about it). Similarly, Kramer has the gall to be proud of his karate accomplishments, regardless of the fact that his opponents are children. Shameless is too mild a word.
George's Best: He Displays Empathy (But Not Very Often)
Interestingly, George is the only one of the four main characters who has displayed, infrequently though it may be, bouts of compassion and empathy for other people. He attempts to convince a stranger not to inflict physical punishment on her child, only to be rebuffed by the mother (and assaulted by said child soon after).
In "The Marine Biologist," George attempts to rescue a whale whose blowhole has been blocked by Kramer's golf ball — although this act is motivated by the woman he wants to impress and he doesn't feel guilt or regret even after she dumps him for faking his scientific credentials.
George's Worst: He's The Eternal Cheapskate
George would rather not spend money if he can help it: this is not dependent on how much he has in the bank at the moment, but on an innate sense of cheapness that exceeds human understanding. When the gang goes to a formal party, Elaine asks him to buy some wine, but he responds that Pepsi would be more appropriate for the event.
Similarly, George is infuriated that nobody notices his tipping, so he tries to skim the jar to retrieve his lost funds (and gets caught). On yet another occasion, he complains about not receiving his Twix due to a faulty vending machine, which was a little too much for such a cheap bar of candy. Finally, there is the matter of the toxic wedding envelopes and poor Susan.