if I remember correctly, the PS1 version of Earthworm Jim 2 never came out in the US, so the Saturn version was the only "next gen" version of the game over there.
Anyways, I pick Rayman , Gex is pretty good on the 3DO but I don't think its in the same category as Rayman in terms of its design, not to mention Rayman isn't all about "attitude". Earthworm Jim 2 is alright, though I have to say Im not a huge fan of that series in general (huge fan of Aladdin on the Mega Drive)
Would've gone with Rayman if it was just a tad easier and didn't force the collecting. EWJ2 is pretty solid and nostalgic for me. Never played Gex though, looked kinda lame back in the day but gameplay is probably above average.