I'll go with popular opinion and say "Yesterday's Enterprise". I remember being in Secondary School when that was shown here in Britain, (that's High if you're American) and most everybody who knew I was a Trekkie, came up to say how great TNG had become lately. Didn't seem to require any knowledge at all to understand it. The Tasha Yar alive/dead stuff. Time altered. Two Enterprises. Well-written and unexpected, given I later read how many cooks were involved in the script. It shoud've been the typical Hollywood disaster being pulled in different directions.
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Somehow they manage to fully negotiate almost everybody from the original crew, into that version of Generations. George Takei's Sulu the notable absence, after several failed rewrites to try involve him and the Excelsior into the plot. It's okay though. He kissed and made up enough a few years later, to appear on VOY. As before David Carson directed, although Leonard Nimoy had input as a co-producer from the beginning - the key person who turned it all around.
Second Next Generation film in 1996, would have to be a sequel to Conspiracy. That's another one I remember watching on an endless loop, especially when I finally saw it on video uncut. The film involving the Enterprise going up against Starfleet, protecting the Federation is a massive hit, having overt horror aspects and TWOK ship v ship style action. The Enterprise-D went down fighting here.
That left the Borg making a difficult third entry a lot easier in 1998. As before, Jonathan Frakes directed both in a row. Once they were out, that was basically it for TNG's popularity. They had played all the aces and a fourth film only ended up disappointing. It turned out to be feature Q as the villain, a plot that finished Data's story with him becoming human, and then in an emotional ending - dying. That send off didn't fair as well at the Box Office, but was generally enjoyed by fans. Positive reaction around enough for Paramount to see what mileage remained beyond TNG.
It's now 2004 and to improve the fifth, a few TNG cast members notably Patrick Stewart, agree to return and handover to a mix of Starfleet characters who've jumped ship from DS9 and VOY. Bryan Singer fresh from X2 directs. It turned out great seeing O'Brien back aboard the Enterprise and on the big screen. It doesn't fair any better than the last film however, but fans got a kick out of seeing the characters from later spin-offs interact and it brought down a curtain on the whole Berman 24th Century era.
Amazingly, Star Trek Enterprise ended up being cancelled twice. Once in 2005, then again in 2006. Returning retooled, after a several month absence with a Fifth Season that lasted for 13 episodes on CBS no less. Ratings weren't shabby apparently. Jeffrey Combs playing Shran became a regular crewmember. William Shatner guest starred as "the Chef" in a two-part episode to celebrate the 40th Anniversary. The show went on to be loved by fans, and are still campaigning for a motion picture end to it. Partly due to it leaving us all hanging with THAT cliffhanger! You know the one I'm talking about...
Oh and JJ Abrams made a Superman reboot, which turned out to be a complete and total piece of crap. What was he thinking? He made good on his probation though, enough to turn it all around with Mission Impossible III.