Complete realism is kinda hard to come by in video games... he knows that, right?
Anyway, I, too, recommend the Dawn of War games.
The first game and its expansions are more traditional RTS with base-building and more or less elaborate tech trees, and it kicks an ungodly amount of ass. All you have to do in regard to resources is plonk down a few generators and conquer and hold strategic points as you spread across the map. To be able to play all the races in multiplayer you need to own the specific game/expansion that introduced them, but to my knowledge there's a complete Dawn of War anthology available for a decent price. Oh yeah, and this is important: Do not install the last expansion, Soulstorm - it's an unbalanced and buggy mess with rage-inducingly frustrating changes to gameplay.
The second game is also good, but not everybody's particular cup of tea. There's no base-building, all your resources are now mined by capturing and holding strategic points and nodes. The game is more RTT (real time tactics) than RTS and employs a cover system, so you need to choose your approach to any skirmish carefully and with consideration to the terrain, otherwise you'll probably get smashed to bits. All in all the game makes up for the loss of base-building by putting a larger focus on squad micromanagement. Also, killing enemies awards you special points which, when you accumulate enough, allow for one of four special goodies to be called to your aid (special attacks or support units).
The singleplayer aspect also sports a fair amount of RPG elements, the most noticable being in-game loot drops and a leveling and upgrade system for your squads.