I think MTW does an excellent job of raising the bar without cheating too much. In all the other strategy games I played the AI either rolled over and died after a while leaving you unchallenged (Sim City and Railroad Tycoon), or else recurred to massive cheating (Civ3, which has been described on its forum as it's like playing against a evil retarded person).

On the other hand some amount of cheating is necessary, since the AI is no way as smart as we are, and if it was then it would use all the exploits we know and love...