First Contact is the best one. It has so much energy. It's fresh and different from what we've seen before. I love the character interaction in that film. Everyone gets a moment to shine. Every cast member is at the top of their game, even regarding their fitness (Frakes for instance, in his best physical shape). They included everything that I associated with the show. Even Barclay shows up. And the EMH cameo is great as well. And the Defiant as well.
First Contact did what Abrams & Co always talk about. Take all the vaguely familar elements a casual viewer could remember about the show(s) and put them into the film. That's why I always use that film to introduce other people to TNG, and it has never failed.