It's not just about pitch, it's also about young vs. mature, soft vs. rough, nasal vs. bellowing etc. The fact is, a lot of the younger guys who jump at the chance to volunteer voice-act in something like this are on the wrong side of some of these things.
The entire cast of the game is military personnel, and including small parts, we're talking about quite a few male characters with voice parts. Let me see what I can remember:
Greg (main character)
Conlod (sidekick)
Caningam (Greg's squad leader)
Marvy (main villain)
Jarvis (Marvy's flunkie)
Espilon (good guy commander)
Carse (true villain)
Narrator
Greg, Conlod and Marvy are all young and have typical medium range voices, and typical young guys can do the parts just fine. After all, sounding normal makes them possible to identify with, right? Jarvis, Epsilon and Carse, however, all sound pretty damn tough in their own ways, and the latter two are inescapably older. Caningam is also halfway there, sounding distinctly like a late 30's/early 40's squad leader who has been in the military all his adult life.
Do you HAVE to make these guys sound mature and manly? Well, I guess not. Suffice to say, though, you want something unique, and getting masculine voices for these guys would give a dub its spice. Coming up with an a good alternative would likely be even harder.