The Justice League would finally have another decent member besides Batman.
I would much rather Mewtwo join the only good super hero team (the Teen Titans)
This post is so cancerous. Wow.
Green Lantern (Jordan, Rayner), Green Arrow, Martian, Flash (Both of them), WW, and Supes are incredible characters and have had WAY better legacies than 90% of comic book characters.
Young Justice > TT
Well, just a few pointers:
Jordan was badly managed. They botched so hard his change of alignment that they had to bring a Deus-ex-machina explanation for it.
There have been more than 2 Flashes. I know most people know only Barry and Wally, but the first Flash (the Golden Age one) is Jay Garrick. The fourth flash (short-lived) is Bart Allen, Barry's nephew.