5 years and I am still hooked on EE, the Single player is satisfying while the multiplayer is simply addictive.
EE and its expansion provide you with 7 or 8 campaigns and of course, the skirmish/melee option.
There is a wide selection of units, which you can mix and vary to suit your needs and the computer AI is never really predictable regardless of how many hours you may spend fighting them.
Scenario editor is also great, once you learn triggers, endless fun, while playing other peoples scenarios online, including warcraft classics like tower defense.
It was a hard job to pull off creating a game with so many epochs, from clubmen to around 50-60 available aircraft, It is mighty impressive while being fun.