I've found that it's hard to find a good one. Post Scriptum looks promising but some reviews say how unoptimised it is. It doesn't even have to be just infantry based, tank/sub/ship/plane etc.. I quite fancy Silent Hunter 5 but again It's got mixed reviews. I'm sure something will come up.
As far as i'm aware Silent hunter has always been fairly liked in general... Not heard about Post scriptum... War Thunder's always an easy choice with lots of different choices (Planes, tanks, boats i think?) Might be worth a look if you've not tried it out yet?