Finished Legend of the Galactic Heroes last night. I wouldn't say this is my favourite anime, but I'm having a hard time thinking of a series better than this. I doubt it's going to "ruin anime forever" for me but it's definitely going to leave a lasting impression.
The show is fantastic, but it takes some commitment, and that's why I hesitate to recommend this to everyone. It's 110 episodes long, has very little humour, and most of the show consists of people sitting down and talking, standing up and talking, or drinking tea and talking. But if you have a decent attention span and are willing to get familiar with these characters and immerse yourself in the world, those scenes of two people sitting in chairs chatting it up can be some of the most riveting animated scenes you've ever seen. It's a wonderful character-driven story that will take you on a journey filled with military strategy, politics, manly space-emotions, and really leave you wanting a cup of tea. Check it out sometime.