Pretty good, but needs improvements.
The levels are well thought out, I think, especially the flying fortress level, that was very cool, I mean, in how many games do you get shot at and, to avoid getting shot, you can jump over the edge of something that's flying hundreds of feet in the air! :)
The bosses were a nice touch aswell. Especially MODOK, if it is actually him, and even though he wasn't in the film it was good to see a familiar 'face', (forgive the pun but I couldn't help it =D )
It could maybe do with a free roam mode, like Spiderman 3, but maybe not as rushed as that was. (ie: awful voiceovers, and very repetitive at times)
If they did put one in the sequel, and I hope there will be a sequel, along with some other minor improvements, such as more diverse missions and more unlockable content, then I would definitely rush out to buy it when it comes out.