Just for once I'd love to play a game that emphasizes realism at the cost of game balance. Because constant focus on the latter in pretty much every game makes for a lot of ridiculous and suspension-of-disbelief-killing situations like a group of soldiers with chainguns shooting down from the sky an armoured FTL-capable Battlecruiser, or small bats dropping swords and a metric ton of gold from their "inventory".
Realism is unbalanced, but guess what, the real world is also unbalanced. I want to play a game reflecting that.
I'm pretty sure you wouldn't want to play that game for long. If you want the real world, you know where to find it. People play games to have fun. To some degree (but much smaller than most people think), realism increases fun, but when it makes the game frustrating, boring and unwinnable, it's bad.
But you can make great games with more emphasis on simulation. For instance, Operation Flashpoint/ARMA(?) or the original Rainbow 6, where firefights are absolutely deadly.
Realism is unbalanced, but guess what, the real world is also unbalanced. I want to play a game reflecting that.