So two games I have played that I love are Panzer Blitz and Panzer Leader, Blitz especially because you can play as the Soviets :). They were made by Avalon Hill in the early 70s but they're not impossible to find online. It's flawed (for example, basically no aircraft which isn't realistic for WWII), but overall I really love the mechanics of it. If you get it, I'd recommend reading up on alternative rules online. People realized early on you needed to modify the standard rules to make it play better.

I've also heard very good things about Squad Leader but never played it.