Out of that list I would go for X-men.
I've got an IM and an Avengers at my house. Both get played a lot. Next out my house played as much as those two would be my Met. Since it isn't on your list I vote for X-men since it's the one I desire the most next. I have a ST and if my wife would let me, I would trade it away for an X-men in a heart beat. Just can't get into it as much as others do.
I like X-men because it has some great flow but also has those stop and breath moments. I prefer the Pro though but would go for an LE at the right price. I just hate the LE Iceman ramp. It comes in handy during the game sometimes but it just doesn't please my eye.
I like WPT but it's a bit to stop and go for my liking. Some really cool rules though. HS2 is great as well but just not deep enough to keep me engaged for very long. Great for a larger collection though.