I would say the Spider-Man trilogy but it has its flaws klike the constant screaming women, the fact that those movies became the cliché of what a super-hero movie looks like (the hero gains his or her abilities, have a love interest, a vilain appears or gains its abilities too, and they fight, most of the time in front of the love interest), or the really bad depiction of Venom by Sam Raimi who didn't like tye character (and who always been a favourite of mine).
Same for the Matrix trilogy too. And also Matrix Reloaded reminds me the death of Michael Jackson, since I was watching the movie just two hours before his death was announced, and was interrupted by the megavideo limit of 52 minutes. This has nothing to do with the quality of the trilogy, but I can't enjoy watching it.
Since Star Wars is an hexalogy, I can't put it here.
Never watched The Lord Of The Ring, I was more a Harry Potter fan, so can't put it neither. Nor Indiana Jones.
So I'll just go with the Iron man trilogy. Always fun to watch rich people fighting each other for make more profits