thats a tough one because these days every show that keeps having extra seasons usually starts off good but gets worse and even unwatchable later on.
- Greys anatomy (i was the no.1 fan, but have been very dissapointed especially with this last season).
- Weeds (had a great start but again the last season wasn't anything to write home about)
- Prison Break (i agree with you, i think season 1 was excellent, season 2 was okay, i couldn't go past that because it was just getting annoying)
- 24 (just as above i thought the first season was excellent, the second was okay, after that i couldn't stand jack baeur it's like they made him superman or something, i just couldn't stand it anymore lol!)
shows that in my opinion got better towards the end:
-sex and the city (the series got better with time and ended just at the right time at its peak, unfortunately for me the movie really sucked)
-friends (was always funny but i loved the last few seasons more)
-Lost (i'm the no.1 fan of this show, however no spoilers please because i haven't watched this season yet, i want to watch it all in one go at the end of the season....can't wait, it's the one show thats on now that i think just keeps getting better!)
ummm cant think of any others now...and yes i'm a recovering TV JUNKIE, i could talk about tv all day long