Either X-Men or Batman. X-Men has fun characters and I really like the Magneto/Xavier relationship. Then again, Batman has Harevy Dent, who is my favorite comic book character. Add in Ra's, Talia, Scarecrow, Bane, and Joker, that's hard to beat. My vote goes to Batman as I like the Batverse (Overall) and am more familar with it than the X-Men to begin with, but X-Men scores second place. I also really like Tony Stark, but the 3rd movie, albeit hilarious, felt really odd. It didn't fit in with anything in my opinion. It knabs third place while Spiderman scores the last. I remember enjoying those films as a kid and they are still good, but I don't see Tobey as my Peter Parker at all. I like the films though and love Topher's Venom, but compared to the others, Spidey problem gets last place.
Depending on if (although they most likely will) Thor & Cap get a trilogy, I can easily see them topping the list. I loved Captain America and Thor 1&2. Winter Soldier looks awesome, as well.