Three games that really wowed me. First one is old, second just got its third, kickass expansion, and third one is old, and has never been successfully replicated.
First one was Privateer 2. From the FMV cutscenes, to the 3d graphics, to its massive size on three CD's, plus its cool menus with liquid buttons and wide ship and component selection and the free-ranging areas you could fly in, it hooked me with I was a little child and hasn't let go of me. Its a shame you need DOSBox to run and install it though.
Second is Sword of the Stars. I pirated it when it first came out was bored, deleted it, pirated it again when the first expansion was released, deleted it again, did the same for the second expansion, except instead of just deleting it I deleted it then bought it off Impulse when the Ultimate Collection was released that had the game and both expansions, and I just bought the third expansion, Argos Naval Yards, which has some cool new toys for you to use in your quest for galactic power. It has excellent AI, a rich and complex backstory, unique and different races, plus it has some of the best combat I've ever seen in any strategy game. It just rocks.
Third is Total Annihilation. Realistic LoS and weapon modelling (terrain WILL block your LoS and weapons fire), excellent explosions, plus it has unit variety that puts Supreme Commander to shame, and its only real successor is Spring, which doesn't quite have the same charm as TA does.
