Big game companies almost always turn into a giant money farm. And we can't blame them, who wouldn't want more money? The beginning of big game companies like Blizzard, EA, Infinity Ward/Treyarch, Bethesda, etc etc, are always filled with fun games. Warcraft, Battlefield 1942, Morrowind, Call of Duty 4, etc etc, those were the best, and always will be. But as they get larger, they have to appeal to more users, so the games get simplified, or developers try new things that they *think* will improve gameplay, but doesn't.
Now that doesn't mean these newer games are bad, far from it (Skyrim, BF3, Mass Effect 2, to name a few examples), it's just not the same as the first ones, and those were the one that gives the best memories.