They Should have just called him Kramer
Just make it a spin-off. It probably would have worked better. Some of the people from the Seinfeld universe could stop by.
Same for the Bob Paterson Show. George Costanza as a motivational speaker.
I'm somewhat surprised Jason Alexander never found his legs on another show, George seemed like the most likely candidate to lead a show although I guess it's tougher to laugh at a lead character.
Kramer was kind of a one truck pony. He was hilarious in a small role on Seinfeld but having him bust his arse every 5 minutes as a lead character got stale real quick. And lets face it, the bumbling P.I. who is somehow successful has been overdone.
You're right. Christopher Lloyd's Jim Ignatowski on Taxi is one of the funniest characters in TV history. But you couldn't do a whole series around him.