Yeah, I'm late, but whatchagonnado?
Well from a visually standpoint which do you think looks better?
If Mario looked better, I would say this is unfair because Mario is on better hardware... BUT, for some reason dispite Gamecube's visual advantage over Ps2 R & C seems to look better. So R & C wins this by a land-slide.
From a technically standpoint which do you think looks better?
(runs to look at videos)
R&C looks better, Mario looks more fun, but fun has nothing to do with this graphics question. I'm sure R&C pushed more polygona, and if not, Mario's Frame Rate is 60 FPS while R&C's is 30 FPS takeing away half the polys Mario could have had.
When they are both released this year which do you think will be the superioer game?
This can't be answerd without my bias.. so I will go with the game I'm more hyped about, Mario.
And will Ratchet and Clank be able to put a dent in the mighty plumber's armor?
Howso? In sales?
HELL NO 
But I do think R & C may set the standards higher for a Mario platformer. I can only see R & C hurting mario if mario hurts itself by being crap.