The real question is this: What are we judging it against? What do we consider the best trilogies because truthfully, I don't think there are THAT many trilogies so it may get there just on the strength that the pool isn't deep. Back to the future trilogy, bourne trilogy, matrix trilogy, star wars, lord of the rings..is that it or am i missing something?
The Man With No Name trilogy (A Fistful of Dollars/For A Few Dollars More/The Good, The Bad & The Ugly)
The Three Flavours Cornetto trilogy (Shaun of the Dead/Hot Fuzz/The World's End)
Spider-Man trilogy (Spider-Man/Spider-Man 2/Spider-Man 3)
The Mexico trilogy (El Mariachi/Desperado/Once Upon A Time In Mexico)
Evil Dead trilogy (Evil Dead/Evil Dead 2/Army of Darkness)
Infernal Affairs trilogy (Infernal Affairs/Infernal Affairs 2/Infernal Affairs 3)
The Vengeance trilogy (Oldboy/Sympathy for Mr. Vengeance/Sympathy for Lady Vengeance)
THe Millennium trilogy (The Girl With The Dragon Tattoo/The Girl Who Played With Fire/The Girl Who Kicked The Hornets Nest)