Transporter 2 is a masterpiece of slap stick comedy. I read somewhere comparing the bit on the Jet Ski trying to catch the cure to a Buster Keaton bit and it felt totally apt. The movie is almost like a parody, to the point where Leslie Nielsen could've played Statham's role and you wouldn't need to change it up at all.
Transporter 1 is a fun action flick, I guess it's important for establishing Statham as the action hero while Arnold and Sly went into hibernation and Diesel and Johnson hadn't found their footing yet.
Transporter 3, eh. Olivier Megaton is a hack. This shouldn't have been a Transporter movie. Given the premise of a driver who can't leave his car or he'll explode, this could've been a high concept classic with the right director.