I'm a Star Wars fanboy so my list is extremely biased, but there are others that I LOVE.
5. Anakin Skywalker/Darth Vader Excl.
4. Green Hulk
3. General Grievous
2. Obi Wan Kenobi
1. Captain America Exclu.
Runner's Up: Lurtz (really great sculpt, but character wasn't important enough for me to keep and display), Darth Maul (another great sculpt/design, but just monopolized too much shelf space because of the pose), Darth Vader (great PF, but it leaves more to be desired, and you NEED the Obi Wan for it to look right on the shelf), Doom (just awesome design/pose overall, but I'm not a big enough fan to drop that kind of $$$ for him....I tip my hat to those who are lucky enough to have him though)
~~Grievous is the only one on my list that I haven't owned at some point just because I missed the Excl. order, and I haven't been properly motivated to track one down. The Hulk and Lurtz are the only ones that are no longer in my collection due to trimming due to space issues. They spent more time stored in the closet than than they did on a shelf during my possession.