Supreme Commander is not exactly difficult, but utterly exhausting. You'd start with a single fucking robot. You'd get a base up and running, spread out, take over all the nearby resources, skirmish with some minor enemy forces, and then take over one of their outposts. And then the map would expand, and you'd have to build an air-force and navy and take over about ten tiny but heavily-defended islands. You would wear down the enemy fleet guarding the islands, and then use cruisers or artillery to get rid of all the SAM sites and torpedo launchers, and then close in and level everything. This would take an hour or two. And then you would be informed that your base was about to be attacked by about a million tanks, and that you had fifteen seconds to prepare. And after dealing with the attack (hopefully), the mission would REALLY start; the map would expand again and the main enemy base would become reachable. The first step is to take over the whole map, and surround the enemy base. And then attack it with everything. After launching three unsuccessful air attacks on it, and then shelling it for an hour, and then making a half-dozen combined air and ground assaults, and fighting off constant airborne counter-attacks, I would FINALLY crushing them with mobile missile launchers. And then the next mission would start, and you'd have a single fucking robot to work with, and I would take a three-week break from the game. Nothing about it was hard per se, but there came a point where it just wasn't fun any more. That game only had fifteen missions, and if it had had any more than that, I might not be alive at this moment.