The nature of business is to take something that is popular and either copy it or drag it through the mud until it's completely lost all aspects of being fun. Case in point: Mario was one of Nintendo's very first characters and he became their spokesman.
Countless games later, he's one tired old plumber and you're tired of saving princesses, racing and brawling. They've given him a brother, an evil twin and been in 3-D. They remade the same game for current generation gaming systems and have even given him a reboot.
Sony has lived and thrived on Sonic the Hedgehog. This character came around when there was still 16-bit Genesis and he's been going strong ever since. Sony stopped making gaming systems, but that hasn't stopped them from bringing out the hedgehog year after year. They need to give him a break for a while and let the brand cool down.
There's only so much you can do with a hedgehog that runs really fast. This was a great franchise in the 16-bit times, but nowadays, it's too simple a concept. It's time to retire.
While we're enthralled with Assassin's Creed, Call of Duty and Prince of Persia, it won't be too long before they're going to get tiring as well. Thankfully, developers are wrapping up the story lines on franchises like Mass Effect, Gears of War and God of War, but that doesn't mean they're going away. Mass Effect was huge and recently finished, but don't count out a different style of game or game with a new protagonist coming out in a year or two.