Isn't this poll in the wrong forum--shouldn't it be in the General Forum?
Anyway I vote TNG. It isn't that I'm that crazy for "All Good Things," but it had a decent and open ended finale.
TOS didn't really have a finale--it just ended.
ENT's finale was a mess.
I don't think I really recall DS9's finale given that I had largely abandoned the series long before the end and saw episodes sporadically. I remember Odo staying with Founders in the great link and Sisko disappearing in a fiery chasm or something. I think I recall Kira and Jake looking out a station window at the end.
I never saw VOY's finale because even more so than DS9 and ENT I wasn't interested. You couldn't pay me to watch VOY.