It seems like most games that aim for realism are very unfun (piss off, spell checker, I say it's a word now). Not many games out there are realistic at all, and probably every single one of them has at least one unrealistic compromise made in the name of fun or playability. Maybe it's finding gold coins in freshly slaughtered bear carcasses, stumbling upon ammo for your arsenal of guns on alien worlds, or medic packs that can somehow heal gunshot wounds caused by tanks, games have to compromise a little somewhere or they turn into horrible chores. Games that forget this or try to branch out usually end in failure or end up not being as fun as they should be.
Take GTA4 for example. If you truly wanted to experience the game, you had to take women on dates, friends out to bars, etc. Doing this would improve your relationship with them, while snubbing them lowered their liking of you. Sadly, not answering your fucking cellphone while you're in the middle of a high-speed chase or getting shot up by Russians and being late when picking them up means you just lost some cred. Or maybe you were picking up a date when your smelly cousin calls to go shoot pool- whoever you ditch will hate you a bit more. While I hope these seemingly minor transgressions wouldn't lower your "cred" with some major characters to the point where they would stop moving the plot along (I never finished the game, so I can't say), it still disagreed with me. It felt like instead of playing the game, the game was playing me.
That all said, I'm making a strategy game. A game with a fairly large scope as it is: galactic warfare. I believe such games have to be mostly based in (some sort of) reality. However, some methods of warfare may totally break the multilayer experience. Take technology, for example. History is filled with examples of a warring faction being totally decimated by another with superior technology. Pointy sticks < swords < guns < tanks, etc. Realistically, if your armada armed with pointy sticks goes up against a foe armed with guns, you're going to lose, and badly. You might not even have the time to reverse engineer their technology before being wiped out. One way of looking at this is technology research is a vital part of these games- you can't neglect it any more than you can neglect maintaining a sizable army to ward off foes. Another way to look at it is that you will make a few mistakes when playing each game. Should you automatically lose the game if you make a mistake and your opponent doesn't? "Fun" says no- you should get a chance to come back. However, somebody has to win the game eventually, and it can't just be based on random factors- skill must have a part in it.
Man, I seriously don't know how game developers do this.