sjvessey makes some very good points about the way people are with entertainment. Tastes do indeed change (the state of the world influences this heavily). Star Trek is already limited in the fact that its generally considered a sci-fi/action/drama franchise. The sci-fi should merely be a backdrop, the action and drama (particulary the drama) could go a lot further than it has.
Enterprise had an amazing opportunity to return Trek back to its roots. Sadly, they have centralized the series around a temporal cold war and conflict with the Klingons and other major Trek species. Exploring strange new worlds or dealing with other incredible and mysterious alien life-forms are too far and in between in the new show. The imagination is lacking, and it shows every Wednesday night. It feels too much like previous series. In the words of William Shatner when he commented on the current state of the franchise, "It's old hat."
When I look back at TNG and see some of those "thinking" episodes like the one where Dr. Crusher investigates the death of a Ferengi scientist who discovered metaphasic shield technology, I realize that once upon a time, the Paramount folks knew they could do so much more with Trek than "warp speed" or "shields down to 20 percent." Indeed, that series gave its viewers much to identify with.
Nemesis could've and should've been something else entirely. It could have been a thought provoking mystery that twisted your mind until the very end. It could have been a suspense thriller involving more of the characters, and less of the ship itself. Any number of things, but my point is that Paramount needs to take time off from Trek, cut the new series short (I say no more than four seasons), and rethink their franchise strategy for the latter part of the current decade and into the next one.
Most important of all, Paramount should pay more attention to what its fans want. If you please the current fanbase with what they want yet offer something more that the mainstream can appreciate and enjoy (like what TNG attempted to do), then you will have sucess and an even larger fanbase than before.