If anyone hasn't listened to Moore and Braga's Commentary for Generations on the Blu-ray release, you should. It's hilarious. It's one long apology for screwing the pooch when it comes to the movie. Not defining the Nexus as deeply as they should, lackluster end to Kirk and the ENT-D, crafting a story about death and mortality and failing to present that as deeply as they intended and Soran's motivations. Brilliantly summed up that their reach exceeded their grasp.
First Contact was done by the same people worked on GEN. Berman, Braga and Moore, and it was amazing improvement. Surmised up what TNG needed to be as a movie for theatres: a go get'em action/adventure series with the character's the fans of the show loved and general audiences could appreciate. I think about what Pirates of the Caribbean series has done and is very popular and has survived to make numerous successful movies and more to come.
Unfortunately INS decided to take huge steps backwards and hash out a story that the audience had seen time and time again and was ultimately what doomed the franchise for films. The story of a people oppressed and victimized for their resources (usually brown people) by white people(Admiral Doughtery and Ru'afo)has be rehashed to death and is uninteresting. No one cares because we know how it ends. Something like Avatar which made 2.7 billion is theatres with the same story as INS, Pocahontas, Dances with Wolves and Fern Gully; is a different story. Avatar was a success because the story of exploitation for natural resources is third in line to the attention of the audience. Whatever resource the villains in Avatar were mining, you and audience forget about because you are so distracted by the visuals, landscape, main character's drama and the whole adventure happening on screen. The conflict over resources is just something to have a big battle at the end over. INS feels small, is presented small, and is ultimately forgettable. They couldn't even spring for brown/blue/fairy people for the ENT-E crew to save. Just a crowd of unsympathetic hippy white people who i think i saw in the DS9 season 2 episode "Paradise". A go get'em action film with a grand adventure would've been a good follow up to First Contact. To be be fair though. INS flies it just doesn't soar, and it certainly doesn't hit warp speed.
Lastly NEM I think was the last chance to get the public's attention in Trek but the damage had been done. VOY closing out it's meandering series with a whimper, and ENT launching it's first unaspiring season. NEM's biggest flaw is that it's biggest catch to audiences and fans is "come pay see the TNG crew in a movie". And that sucks. Star Trek X could've featured any story with the TNG crew and i still think it would've done poorly. They tried for a balls to the wall action film which the fans and public responded to positively in FC and the Dominion War battles, but it wasn't enough. Maybe if there wasn't a 4 year gap between INS and NEM, and maybe if NEM was a bigger picture (in the sense that we see more of Romulus outside of sets, and more of the universe the crew inhabits) there could've been a greater rewatch effect and resulted in more ticket sales. The Star Wars prequels all feel like big pictures when most of the shooting takes place on green screen. However the world of Star Wars feels so much bigger because there is so much to look at. NEM feels small by comparison to something like Episode I and II. One of the benefits i like in JJ's film. Scope and scale of the film feels large.
With a smarter producer, better allocation of resources and tighter control on screenplays that would be sure bets to make as much money as possible. I think the TNG film franchise could've flourish. Look at the James Bond series. It has 23 offiical films and spread across 50 years and they are still making them and they are still making money. While there have been a few films that haven't performed as well by Bond standards "On Her Majesty's Secret Service, Diamonds are Forever and The Man With the Golden Gun" they weren't complete failures. Look at the Roger Moore and Pierce Brosnan eras. With films like "Moonraker, Octopussy, A View To a Kill, Tomorrow Never Dies and Die Another Day" all these films have issues in one way or another but the producers filled them and marketed them with things they know the audience liked and wanted to see. Moonraker is an obvious attempt to cash in on the Star Wars craze in the late 70's but it made the most money in the franchise until 1995 when Goldeneye was released. Die Another Day is way over the top but it's filled with all the tropes and flashy things audiences at the time wanted to see.and before Casino Royale in 2006 Die Another was the highest grossing Bond film. What I'm trying to say is doing the "right thing" (Rick Berman) : keeping the franchise as close to the original vision of the show and Roddenberry's ideas, is not always "smart thing" (JJ Abrams and Bond producers) : making your films the biggest money makers you possibly can.