Halo 3 ODST or Marvel Ultimate Alliance 2? Which offers more for my buck?

[Platinum Ice]

Alright, so I've got enough cash to buy either MUA2 or ODST. I loved Halo 3, and Firefight looks pretty fun. I have all the Halo 3 map packs to date though, so the map packs included aren't really going to boost the value that much. I've heard Ultimate Alliance is awesome, but I'm not the biggest fan of button mashers. I don't hate them, but I just can't play them for hours on end like I can CoD4.

Which should I get?

Feel free to suggest any other game out that I should get instead.