You can compare this game to the Sudden Strike series. But: It is way more polished, offers more realism, more variety in game play, a cool campaign system with random maps and historical mission, campaign wide experience levels, a nice upgrade system and tons of WWII flavour to spare.
You will never forget the moment your troops run into a tiger for the first time.
You will never attack with your tanks without infantry support a second time.
It's right between an RTS and a Wargame. Realism enjoyable.