Actually I haven't seen 2. But I have seen xXx and that's pretty close I think. After watching Fast Five, I felt like I needed to watch all the other because I had no idea who these characters are. It's like watching the Avengers with only having watched Iron Man 1.
1, 2, 4, and 5. Tyrese / Ludacris and others are introduced in part 2. 3 was in some stupid alternate dimension. "No", you say? Well it should have been. Did I mention Fast Five was one of the most ridiculous movies I've ever seen (not in a good way)?
They had no reason not to, plus given the post credits scene it was basically all but confirmed that a fast 6 was coming.
I hate to accuse anyone prematurely, but even in his earlier wrestling days - his physique was never bulky like that. He was a taller, muscular guy, but he was never bulky, like say the Ultimate Warrior or Brock lesnar.
I was pleasantly surprised by Fast Five so I'm not going to be cynical about this one. They deserve at least one sequel. Plus, it was nice to finally see the Asian dude get the girl.
You should watch 1 obviously, 2 (Tyrese/Ludacris/Eva Mendes), 3 (Han, but maybe save it for last since that's the way it is chronologically),4 (Dominican guys and Han's chick). Also, Better Luck Tomorrow is a movie that was also directed by Justin Lin and set in the same universe. The Han character was in that movie as well and there have been some cool tidbits in the Fast and Furious movies that relate back to Better Luck Tomorrow. It's a good movie too and I'd recommend watching it, since I like Han haha.