I can't imageine there's anyone who's completed Mass Effect 3 who thinks the ending was satisfying, given the story and themes leading up to it. Certainly, if you've played through all three games -- a time investment of potentially hundreds of hours -- the end was just plain horrible. Much like the boss fights in Deus Ex: Human Revolution that engendered similar rage (although on a lesser scale), it seemed cut from a completely different (inferior) game.
Am I disappointed? Yes. Did it ruin the game for me? No, although it did leave a bitter taste. Do I feel I'm in some way entitled to dictate to BioWare that they need to change the ending because of some Bizarro-World logic that says I'm an equal partner in the creative process? Well, that's just stupid.
Dispite some missteps (ME1's item management, ME2's planet scanning, DLC that should have been included in the core game, etc.), the Mass Effect trilogy was fun, with good writing, interesting combat and more than a few moments that forced you to stop and consider the potential consequences of your actions. And I'm having a blast with the multiplayer, even though I'm not really that good at it. I really can't say I feel like I've been cheated. If you feel that way, I honestly think that says more about you than it does about BioWare.