55. Command & Conquer: Red Alert 2 / Yuri's Revenge (Westwood Pacific, 2000)
54. Warcraft III: Reign of Chaos/The Frozen Throne (Blizzard Entertainment, 2002/2003)
Warcraft was one of Blizzard's earliest hits, launching a game with two long and varied campaigns and plenty of charm and atmosphere. The sequel offered a vastly improved UI and larger-scale battles, and Warcraft III certainly upped the ante too. The total number of playable factions was raised to four (adding the corpse-manipulating Undead and nature-oriented Night Elves) and working some RPG elements into the proceedings - each army gets their own unique "hero units" that power up after defeating foes, carry an inventory of items (like temporary power boosts or potions to recover HP) and have powerful spells that can quickly turn the tide of battles; however, losing one at an inopportune time can quickly put you at a grave disadvantage, too. I wasn't a huge fan of this element as it overtakes a disproportionate part of the game's overall strategy, but the polished design and sheer diversity of the four races make it a great RTS nonetheless. The Frozen Throne is a great expansion too, adding new units for each army, two neutral factions (the Naga and the Dranei), reintroducing naval battles, and of course continuing the storyline from the original game.