Yea, the "realism" or "simulation" label is tricky. I own (or did own, can't remember if I've sold it) Phoenix Command, but never tried to run it. I never bought Aftermath because of it's reputation.
I have run plenty of games with intricate mechanics. While I got started in RPGs with Holmes Basic, I soon migrated to Chivalry & Sorcery and worked through the magic system which is pretty intricate. RuneQuest has it's levels of intricacy though it really isn't that complex. My college friend's home brew, Cold Iron, had some intricate moving parts but it's really not THAT much more complex that RQ, it just looks scary due to some of the technical math in it (exponentials, logarithms, true normal distribution). As estar mentions, GURPS has tons of bits and bobs to sift through, and I never made it very far running it. I did try a sample combat or two with Harnmaster, but it wasn't the right system for the players I had a the time, with a different set of players I might have latched onto it (I certainly had bitten into Harn good and solid, having started subscribing from the start, now I'm almost Harnless...). Burning Wheel has different levels of complexity.
Each of those games made some kind of claim to more realism than D&D, but I'm not convinced you can't run just as realistic a game with D&D.