I actually the first Spiderman better than the other films; William Dafoe as GG was epic, and I thought Tobey pulled off brilliant-but-awkward Parker a lot better in that movie than in the others (where the nerd factor mostly got lost and the angst/emo factor kept increasing until...well, you know).
I think outside of that series, though, most comic franchises have been getting better with each installment/remake; the last Hulk was an improvement (not saying much, but...), First Class was better than most if not all the previous X-Men films, TDK was better than all its predecessors, the Superman film wasn't great but was better than the attempt before it, and Iron Man 2 was also better than the first, IMO.
I think the comic adaptation crowd, as a whole, is just learning how to translate comic material to the big screen better (i.e., you don't have to cater it to violence-loving preteen boys in order to make it a success). It'd be awesome if this trend continues.