We don't need no stinkin' poll. State your reasons.
My pics.
1. The Evil Dead trilogy. Justification: while the second installment was largely a plot repeat of the first, Evil Dead 2's tone was remarkably different. There was a transition from the slight amount of tongue-and-cheek in the first film, to the laugh-out-loud humor of the second. Plus, Ash went from the regular, gee whiz horror victim to one of fiction's most memorable badasses whilst simultaneously being a dimwit in the vein of The Three Stooges. As for the third film, Army of Darkness, there was a total break in plot formula that added to the whole deal. http://www.youtube.com/watch?v=m_I2p50rb6E
2. The Dollars trilogy. Justification: Each film had a unique plot. Each film could be enjoyed on its own. This was more than just a cash cow, it was a venture that had considerable creative talent poured into each piece. This kind of passion over half-assing is rarely seen in the mainstream films of today. http://www.youtube.com/watch?v=pw8mOUEaY-k
3. The Godfather, I and II. Justification: Based of the first and second halves of a book, these films worked so well together because the second part wasn't an afterthought, it was already there. The second installment completes Michael Corleone's loss of his soul; what starts off as evil for the sake of his family becomes evil for no one's sake at all. As for Part III: I enjoyed it, but I agree with Puzo's and Coppola's assessment, in that it functions more as an epilogue than a necessary part of the story. http://www.youtube.com/watch?v=PQBW6G0hSrs
et I loved how thee movies were nothing like the books 
btw I'm tried forgive me for being weird 
he was cool :'(