Can't say it was the best for SEGA though.
I understand Sega were struggling after the Dreamcast, and they hoped Sammy would save them from going out of business... only for Sammy to swallow Sega in its merger, rip them to pieces and sew them together with bits of other subsidiaries into a Frankenstein subsidiary. They gave this monster the "Sega" name, made it make Iron Man and Sonic '06 and Sega's reputation has been shot ever since.
Meanwhile Sammy rebranded themselves as "SegaSammy" giving Sega the top-billing when in truth it was less of a merger and more of they consumed Sega while Sammy remains in charge. I know Sammy specialises in panchinko, working around Japans gambling laws and generally had bad public relations. They wanted Sega so that everyone would see them as the cool blue gaming industry, than the exploits they really are.
What's wrong with Iron Man? I f**cking love that game.
I bought all version of them, even the inferior NDS version.
Also Iron Man was a success.
It's even managed to be in Top 10 game for PS2 and PSP for some weeks.
Its PSP version even got re-release as "Greatest Hits" series due to its good sales.
(A game only can earn this 'greatest hits" title if it meets certain sales criteria within two years after its release).
The sequel (Iron Man 2) and the follow ups (Incredible Hulk, Thor, Captain America) are the ones who could be considered as a failure.
(though I do love Captain Ameica on 3DS but the game was released very too late, few months after the movie's already released).
Don't dish Iron Man for its later follow ups failure.