If you edit in Sony Vegas Pro you can lower the DB of the game audio and increase the DB of your mic by how many you want, so you can mess around with those to find what works for you.

I always play one of Pewds' videos and adjust my footage volume level until it's just as loud as my referal video's audio.

-Download and use Audacity for your commentary.

-Make sure that your input device is your microphone of choice.

-Record about 6 seconds of dead air(sounds you don't want in your commentary(typing,fan,computer humming,etc)
afterwards go to effects>noise removal>get noise profile. (This will remember the noise you don't want in your commentary.

-Open a new file and record your commentary track as you would.

-After you've finished go to effects>noise removal.

Make sure to have these parameters set:

Noise Reduction: 25db

Sensitivity: 3.09

Frequency Smoothing: 400

Attack/Delay Time: 0.15

Click ok(make sure it's on remove and not isolate)

Afterwards go to Effects>Compressor(makes loud noises louder and softer noise quieter)

Make sure these parameters are set:

Threshold: -10db

Noise Floor: -30db

Ratio: 6:1

Attack Time: 0.5secs

Decay Time: 1.0secs

Click ok.

Next go to Effects>Treble and Bass

Set the bass to 3.0db

Voila, you now have perfect audio.

After that, go to file>export and export the file as an mp3.

Most editing software has a "ducking" option for audio tracks meaning that when a certain track has ducking enabled, the other tracks will go down in volume.

No, I just play it on youtube and compare with my ears.

You're a moron.