It's not out yet but still, LittleBig Planet does NOT need a sequel, just more DLC.
SSBM, likely one of the more controversial opinions but Brawl was an overall disappointment to me. Everything got faster and weaker and it just messed up the gameplay too much to be enough fun.
Soul Calibur III. Now, don't get me wrong, I liked that they made SC IV, but it was something of a downgrade from SC III. 3 had a great story mode to it and a fun extensive campaign for your create-a-character, but while adding next to no notable new characters and giving a pile of steaming shit for a story-mode made me wish it hadn't been made at all.
Guitar Hero.
There's a theme to my entries it seems in that all of these games would've been much better with DLC rather than full sequel. Party games, or games with extensive character creation or playable characters that add very little every new game should just make DLC's. I know, SSBM was on the Gamecube before DLC, but still, imagine if instead of screwing with the gameplay they just added a set of all the new characters and stages to download? Plus, they replaced Mewtwo, a Pokemon icon with Lucario, who's not even a legendary, just a giant poser. Soul Calibur, and pretty much most fighting games just need downloadable characters at lower price instead of paying full price for a game that just has slightly better graphics, a handful of new characters, and the story made slashed to piles of poo poo pancakes. As for Guitar Hero? seriously, what's better about any new game? Wouldn't you rather have 1 Guitar Hero game that your used to with ALL the songs along the way instead of having to switch games when you want to go from Trogdor to Through the Fire and the Flames? And Little Big Planet, a game built on user-made content, and all games like that, a sequel makes all your hard work meaningless. Congratulations, what could possibly be in the sequel that they couldn't have made downloadable?
With games like Bioshock, (Haven't played 2 yet so I can't judge yet) there's a lot of negativity over continuing games that stand alone. While I'm all for not extending the story just to sell, as long as the story is good, don't make such a fuss. Just because something was great standalone doesn't mean it CAN'T be continued. While God of War stood alone great, it left me wanting more, just because of how fun it was, and the story added on took the continuity and gave it more intricate twists without ruining the integrity of the original imo. Yeah, it worked amazing as a standalone, but I think it works equally amazing as a series. Same with No More Heroes. If the creator can make a good story, it can be good, but I rarely judge a sequel before it comes out based on whether or not the original stands alone well. Exceptions being of course, Team Ico games. Direct sequels would not work well. But they know that. Downloadable colossi for SOTC though? THAT would be fantastic.