I thought that Sunshine was excellent, up until the last half hour. It's clear that nobody involved had any idea how to end the movie and instead they just gave up and decided it was going to be another Alien. So, in that sense, I agree that it was one of the most disappointing films I've seen.
To expand a bit on my reasons for suggesting it's rubbish:
1. All the uranium/plutonium in the world would not re-ignite anything on the Sun. It's a bit like trying to set the Pacific ocean on fire by dropping a smouldering fag end into it.
2. The grunge look of the ship - Alien??
3. The Holographic room - Star Trek: The Next Generation anyone?.
4. How did the captain of the first ship survive 7 years with 100% burns?.
5. The scene where they blew themselves over from one ship to the other - Dave Bowman did the same in 2001. Rip-off!
6. The 'bomb' plopping onto the surface of the Sun at the end. The Sun is a giant ball of superheated gaseous plasma - it has no real 'surface'. Plus the bomb would have burnt up in the corona.
7. While waiting for the bomb to go off, the scientist has a religious 'epiphany' moment and caresses the wall of plasma. Whaaat?. He'd be vapourised in like, 0.1 seconds.
Okay, it's just SF but should at least have some sense of internal logic and vaguely correct science. Sunshine has neither.