First of all, are you meaning a Real-life comparison, or one made for Video games? There is quite some difference between RL and Video games.
For the most part, I'm kinda like Arlo, My bias tends' to American iron. I'd certainly pick a Garand for myself, It's got a great long-range cartridge (.30-06) and is very accurate, especially for a Mass-produced service rifle. There were Semi-automatic rifles' made by other countries and issued (The Soviet SVT-40 and the german G-41 come to mind) but not as widespread as the Garand.
For Sub-guns, it starts' to become more of a matter of application. The Thompson, in it's various forms, fired the .45 ACP cartridge, which gave each round very good stopping power. But many argue that the Thompson was Heavy and over-complicated for what it was; But having a heavier gun while firing full-auto would help control recoil, thus helping your aim. However, you can compare the Tommy with something like the MP-40, which fired the 9mm Para. There are a lot of accounts' that speak highly of the MP-40, which equipped quite a few of the Wehrmacht during WWII. The Brits' built the sten, which also fired the 9mm(Useful, you could use captured german ammo, If you were running short). The Sten was an emergency design, hashed out right after Dunkirk, but was succesful enough that it's improved versions' were used for some time after WWII.
The PPsH-41 was a good, sound, simple design, that was mass produced and issued in huge numbers. It did have a very high rate of fire(900-1100 rpm.) But it did fire a smaller cartridge, with somewhat less knockdown power than the 9mm or the .45ACP.
For Squad-Automatic weapons' and MMG's, There were so many used we could start a whole 'nother thread on this topic alone. But some have said that the Bren gun (UK) was one of the best LMG's used in the war, and the German MG-34 and MG-42 were two of the first, and best, GPMG's used.
Tell ya what, Bat, since my fingers' and wrists' are starting to get tired, I'll throw you some links' to sites to check out.
http://www.geocities.com/pizzatest/panzerfaust7.htm#mp38 (Good site on German infantry arms.)
http://www.secondworldwarhistory.com/worldwar2_weapons.asp (A general weapons' guide)
http://hk.geocities.com/guncobook/03.html (A lot of good color plates, showing different models, but not much hard info)
At this point, I can merely leave you to pick out the different models' you wish to research, and google them up yourself, Bat-There's quite a few there.
