Supreme Commander is a large scale RTS from 2007 its meticulous design, backed by a massive budget, resulted in a huge amount of depth and strategic diversity, a superb art direction, and innovative quality of life features that streamlined the interface. To this day, Supreme Commander is still one of my all-time favourite RTS games, and I play it on FAF (Forged Alliance Forever) from time to time.
Although Supreme Commander is on the opposite end of the RTS spectrum, it resonated with me, and many LANs of my teenage years were spent playing it. I love the fast-paced rush of StarCraft, the tactics of Company of Heroes, and the intricate micro of Command and Conquer.