Really depends on the games natural audio. In premiere pro I generally have my game Audio set to around -6-12 and my voice set anywhere between 0-3 depending on stuff like how close I was to the mic, what's happening in the game etc.
Look at this. If you are using Sony Vegas on the right side there's that panel that shows you how loud the video is. In the picture there's number 1, there you can fix dB (loudness) on your video. If my game is/isn't loud enough I'll fix it by going down or up with dB. You can see how loud it is by looking at the right bar number 2. in the picture. My game is usually on 60-70% of that bar and my voice to 100%. I found out that this technique works for me the best.
I actually don't use Vegas I use cyberlink pro lol I know random but it's pretty similar idea I thinkLook at this. If you are using Sony Vegas on the right side there's that panel that shows you how loud the video is. In the picture there's number 1, there you can fix dB (loudness) on your video. If my game is/isn't loud enough I'll fix it by going down or up with dB. You can see how loud it is by looking at the right bar number 2. in the picture. My game is usually on 60-70% of that bar and my voice to 100%. I found out that this technique works for me the best.
Hope it helps a little bit. If you don't get it I'll try to explain it in to more details
