While browsing Wikipedia earlier for... Heck, I can't even remember what I went for in the first place... I came across the entry of the unreleased 90's Fantastic Four movie, which got me thinking of other rumored/proposed/cancelled things that looked good or at least interesting but for some reason or another never came out, were scrapped, cancelled mid-production or whatever.
Stargate MMO: I'm still pretty sad that this never saw the light of day. From reading articles and interviews by people working on the game, I was really excited for the game. They even had contests on Syfy to be included as a character in the game, but for whatever reason it kept stalling until it was finally shelved when MGM decided to shelf all things Stargate related. Which brings me to my second list item:
Stargate Universe Movie: After Syfy cancelled SGU and leaving the series on a cliffhanger, it was said that the loose ends would be tied up in one of the future direct-to-DVD movies. And then MGM decided to say "No more Stargate whatsoever". You stink, MGM.
Star Trek Online: Yes, I realize that a game called Star Trek Online did indeed come out. However, it isn't the game that was originally scheduled to come out. Before the current game came to be, another game by another company was in the works that was a very different sort of game. A bit of the original game was incorporated into the current incarnation, but it is still a very different game than the original company had worked on.
Original Power Rangers Season 2 Concept: This is something I can understand why they didn't do, but it was still a pretty neat idea. Originally, Power Rangers was to end, just like the Super Sentai series it was adapted from. However, due to unexpected popularity, it kept going. When the second season came around,
there were originally plans to have new updated versions of the original Dino Zords instead of using footage from the next Super Sentai series. I'm sure I'll think of more later.
How about you? Anything you wish would have been made that wasn't?