Well, this is certainly attaining to my interest, my first post ever in the forums.
I could beat a dead horse and rattle off many... many things already listed, sonic, metroid, mario. But why continue reiterating the same points.
Starfox - The first few were great, even Adventures was still a forerunner, until all that furre sledge was mucked up, and Nintendo tried to cash in on the same cow, thus lumping Starfox in with it's other abused franchises.
Left 4 Dead 2 - I loved the first left 4 dead, even the second one was alright, but it is an expansion pack they expect people to pay full price for. A few new monsters, a few more weapons and one new thing (Melee weapons). Yes they made changes, but not enough for a full priced game, and given Valves track record of taking forever to release an awesome mind blowing game, it feels rushed and unpolished to me, and the price is through the roof for what it is. I didn't buy it till it went to the bargain bin myself.
Warcraft - It was good the RTS games, then the MMORPG, vanilla and BC, then everything went down hill when activitions bought blizzard out, they seemed to have adopted activisions business ethics as well.
EA Sports - personally I've never been a big sports game player, mostly none really. But I am surprised no one has touched this franchise yet. EA sports holds a stranglehold monopoly on the sports game industry (Which is also Illegal as the monopoly violates anti-trust laws.) Only one sports game (A football game I cannot remember the name of) has ever been released outside of EA. All they do is rehash the same game with slightly better graphics and no new innovation, I honestly feel it stagnates more than Sonic could ever dream of.
Aliens/Predator (Aliens vs Predator Franchises) - Again, I'm surprised no one has brought this topic up. Aliens and predators have had some good individual games, and even fought each other in better games, but the series has some awful games, that I have to convince myself are good to justify the prices. Aliens was one of the first horror/sci-fi movies I ever saw in my lifetime, and thus I have always followed the franchise cash in after cash in. The last AvP game was rancid, I pre-ordered it because the original team was rebooting it, or remaking it was ok to start with, but Lance Hindrickson of just about any b-movie fame was attached, following on from the AvP movie plot, then they ruined the predators side of the story, cut the very fun aliens side in half, and extended the boring old marine side. AvP2 from 2000 is probably the pentical of success (I even enjoyed AvP extinction, even though I believe it would have been a better computer game than a console RTS.) But thus far it has been going down hill for all sides for quite a long time.
Black & White - The first game was revolutionary which featured AI with a learning curve, and is still quite unprecedented in that fact. Gameplay was fun and I spent many many many hours (Perhaps days) enjoying the original. I honestly never bothered with Black and white 2 when I heard it focused more on war and less on creature development. Most of what I have researched said it was garbage and gameplay never really fascinated me eather.
Dead Space - Before people beat me to death over this opinion, the games are good. The forum is about franchises and the Dead Space franchise itself (Comics, movies, tie in material) is god awful, made to squeeze precious penny's from the fan base, and also follows on with EA asking for money to unlock content already on the disc, IE day one DLC, which every game of theirs seems to have now of days. I don't agree with this business model at all, that and the franchise is designed to be a big penny pincher. The games are good though.
Gears of War - I played the first one, it was ok at best, but it was envisioned as a trilogy from the beginning, I felt the ending was lacking, and couldn't really stomach gears of war 2. Aside from that the reason this game is on my opinionated list, is because between it and halo have ruined the particular FPS genre Switching between two weapons screen getting blurry with the more damage you take and nothing that can't be fixed by hiding for a few minutes sucking your thumb or thinking really hard about someplace nice, or playing peek-a-boo with masonry. And rendering everything in gritty dirt and dust. Mostly involving an alien invasion at some point. I mean provided Halo and Gears did not have this effect Duke Nukem Forever could have been a by far better game But I do feel Gears is going down hill regardless how many people will not agree with me (It is my opinion after all) and rather than taking just self down with it, it and halo dragged the genre along for the same ride, ruining other franchise and games before they even had a chance.