There have been lots of comic book/cartoon movies made the last few years, and they have been very successful. Transformers (second movie coming this year), Spiderman trilogy, X-Men trilogy, Batman Begins and The Dark Knight (and the earlier Batman movies were also reasonably successful), Superman Returns.
I think it is the right time for these movies now that technology exists that allows moviemakers to recreate cartoon heroes and action without just actors in silly outfits and lots of explosions. Technology now allows for 'live action cartoons' and I for one think it is absolutely the right thing to do. And it's about time the Joes got some love from Hollyweird!