Master of Orion 3. 2 was an amazing game, and is still my favorite strategy/empire building game ever. Then 3 came along with its new "streamlined interface". Apparently making decisions yourself and running your own empire was bad so they decided to make the AI do everything for you. And it was the dumbest AI ever, it did nothing but build troop transport ships, without any troops to go in them. You could supposedly override the AI's decisions but half the time it would ignore you and just go back to building transports.
They also removed all control you had over the combat system, and zoomed the perspective so far out that your ships were nothing more than dots. And just to add insult to injury, they even destroyed the story, totally invalidating everything you had done in the previous game. It was basically "Congratulations, you destroyed the evil race of galactic conquerors. Oh wait, that wasn't their real home planet and now their main force has defeated and enslaved you and everyone else. Sorry."
All in all, the game was only good for 2 things. It made an excellent "Hit End Turn Button" simulator, and a pretty good frisbee. Then I decided its very existence was an affront so I smashed the cds.
Definitely the most disappointing game ever, I was expecting so much after playing 2, and this game not only didn't deliver but actually ended up killing the series entirely.