I have always SP World At War and WinSPWW2 in my hard drive. Even though I know the latter is better considered, the bigger scenarios are not for me... I still prefer chosing a small/medium scenario in SPWaW and blowing waves of T-34s with my Tigers for example. The original SP1 is still really fun to play using Dosbox.
Regarding similar games, don't forget John Tiller's Squad Battles games. I know they are the ugliest in the world (mods aside) but they give a really interesting feeling of close combat in tight low unit scenarios. Unlike in SP, SB games model quite well infantry combat (in a lower level, you can for example change your weapons, take enemy's heavy weapons...) but they are not so good at vehicle combat. If you like a higher point of view of the battle the new Panzer Battles are also really fun.
