Other than when considering controller preference, the multiplatform games are almost always rated better for Xbox when the multiple versions are compared (Unless PC is added to the mix, and then it often wins the recommendation).
http://www.ign.com does do head-to-head comparisons. I dunno if they still do em very often, but they may be a good place to start.
[EDIT]
I just went there, and they do have one for X-Men Legends, but it seems that the head-to-head features are for insiders only (paid subscription to the site).
The entire article is 7 pages long, but here is the Final Verdict from it:
Final VerdictLooking for our overall recommendation? This is the place to find it. We base this final verdict not on how many "sections" each platform has won. It is not a total accumulating in any way. It's about the overall impact of each element; usually features are the most important because they affect gameplay, but the visuals often carry a lot of weight as well.
We encourage you to consider all aspects and make the decision that best suits your tastes.
Overall GameCube Advantages:- Better Visuals than PS2
- Quick Load Times
Overall PlayStation 2 Advantages:- Sharp Display (no blur)
- Ample Buttons for Controls
Overall Xbox Advantages:- Best Visuals
- 720p and 480p
- Widescreen
- Best Audio
- Quick Load Times
The Recommendation: If you're a home theater type, go for Xbox. From 720p to the better sound, it just is better on the senses. If you don't have a fancy setup, Xbox is still the best bet, but GameCube isn't a bad choice either. The PlayStation 2 would be the last recommendation, mainly for the texture warping and displacement issues, which draw your eye away from the action occasionally.
Overall Winner: Xbox
Winner Ranking:1. Xbox
2. GameCube
3. PlayStation 2