It depends on the type of game you're after.
I'd recommend Nuts! from Two Hour Wargames, for the grim and credible feel for squad on squad games.
For something more Heroic/Adventure feeling with a few characters a side, have a look at Amazing War Stories from Rattrap.
For games of about a platoon a side, you could take a look at World at War from Mongoose or Rules of Engagement from Great Escape Games, both nice rule sets. WaW seems a bit more "move and shoot" while RoE is much more in depth with the unit customisation and psychology.