I voted for Tree of Might, but honestly, they're pretty much all winners except for Lord Slug and Bio Broly.
The fight choreography in the first three movies
Goku and Vegeta teaming up against meta-Cooler
Goku getting punched in the junk against Super 13
Piccolo G-checking Vegeta when Broly attacked
Gohan vs Bojack and his crew
I wish Bio-Broly hadn't been so crappy. I love the idea of the weaker characters having to step up and save the day without Goku/Gohan/Piccolo/Vegeta around. Android 18 is criminially underused.
And props to Resurrection of F for finally letting some other characters besides Goku and Vegeta get some real action for the first time in 15 years
My dude Krillin actually shining in a DBZ movie for once