Lord of the Rings trilogy. Peter Jackson knows how to create spectacle.
The original Star Wars (the prequels sucked. End of. Hayden Christensen is NOT a good choice to play Anakin before he was drawn to the Dark Side, should have gone with someone else, but will debate this at a later date).
Toy Story trilogy. None of the films are as weak as another, but the best one depends on your opinion. I loved Toy Story 3, as, after watching the other two, you can see how far Pixar has gone since creating their first epic feature film, and keeping the characters as loveable as they were in the first film was excellent. The final fifteen minutes actually made me cry, because it was a perfect send off to an almost perfect trilogy. No film is perfect, but this one, as well as Toy Story and Toy Story 2, came pretty damn close.