Would the chemistry have still been there without Jerry in the mix?

Who knows? I wouldn't have bet on Julia and she had two successful series.

I think Jason Alexander had two series that failed. One was called Bob Patterson, I never saw it (and neither did most people) but it seemed this character was somewhat like George from the previews.

Jason Alexander to me was the funniest one of the four. Seinfeld more or less retired (basically a billionaire from this show) with Julia Louis Deyfuss being the most successful one of the other three. All I have seen Alexander do is some guest spots on shows (although he should be wealthy from Seinfeld also). Michael Richards just disappeared, probably "cancelled" from that time he made some "racial slurs" on stage at a comedy club.

Jason Alexander was the senior star in Seinfeld. He had the most experience.

It wouldn't have worked. The episode where Elaine and George were alone and had nothing in common would be magnified with no Jerry full time, the glue that held them together. Now the spin-off that would have been fascinating: Kramer, Newman, and Kramer's dwarf friend.