Final Fantasy - Seriously, in the last 2 generations, the number of games has jumped from about 30 on the NES/SNES/PSX to over 80 games all named 'Final Fantasy'. They're milking their sequels/prequels and re-releases worse than Disney.
Pokemon - Sorry but, there's already been 4 versions of Pokemon just this gen, not counting the spin-off games. That's roughly once every year and a half. And if this was a different JRPG, it probably wouldn't be a problem. But these games are massive with development teams in the hundreds and expected to create an entire new world and Pokemon each game. And worse, each game we have to play the same 50-70 hour main game just to get to the actual bulk of the game. I know many people who are just like me, we've given up on the series because we're tired of having to spend MMO level hours doing the same thing over and over.
Tales - Its just my opinion, but this series is getting overdone. And each game has seen almost a 50% drop off in sales as its predecessor. Expectations are very low for the next two Tales games in development that it'll even sell over 300,000. Its going to become the next Suikoden, except Suikoden didn't have the advertising Tales has.
Halo - This one is getting the the point where its sales are going down and even fans are kinda tired of it. But its MS bread and butter so expect another soon.
Sonic - Nothing needs to be said about this one.
Castlevania - Many people will argue with this. But just look at the games that have come out in the last 2 gens. Nearly all of them are SotN clones with little change. Heck, now there's a straight side scrolling brawler on XBOXLive which is literally just ripped sprites from all the past Metrovanias and made into a 4 player game. Even the bosses are ripped from past games. This series has gone well downhill from its predecessors on the NES/SNES/PC-Engine which rivaled other major series in innovation in graphics and gameplay. Not to mention having some of the Konami's best teams working on it. Hopefully Lord of Shadows will change this trend. But considering it didn't sell much more than the past metrovania titles, I doubt it.
The Sims - Really, they've milked this series so much they have to start focusing on other time periods. I think that speaks for itself. What's the point in having a reality simulator when now you can be in the 14th century?
I also argue these series are not over-milked and have not shown a significant drop in quality:
Mario - Some of the best Mario games came out this gen. If its being milked, its being milked in a good way.
Assassins Creed - Why do people keep complaining about this series? Its doing quite well. Each game is reviewed just as high as the last and millions bought Brotherhood. And they'll buy Revelations as well.
Six upcoming games you should look into:
