Oddly enough I think my first Star Trek experience was Star Trek: The Motion Picture. I had seen bits and pieces of the TV series as a kid but never really watched them all the way through. The movie I did and I really loved it (and still do) as a child. I kept thinking how awesome and creepy the whole V'Ger cloud was and the interior of the ship. I still think today V'Ger is one of the largest spacecraft ever depicted on the big screen.
And that Klingon battle theme is the best!