Oh wow, I can't pick one series... like seriously that's impossible!!!
I grew up with TOS and TNG and later came DS9 and Yoyager (for these two I still haven't watched all episodes because this was around the time I started working)
Right now I'm watching Enterprise (finally!) and even if it's very different and you can argue your ass off about continuity to the other series', I really came to love it as well and I'm really sad that it got cancelled just when it's getting good (I'm in season 4, episode 13)