Depend the console,

WiiU i will end with 5 games probably
3DS around 10 games
Psvita around 20 games 
Ps4 around 60 games or more like the ps3.
PC around 20 games per years (indie counted)

Sony consoles? 50+
Microsoft consoles? 15+
Nintendo? 10+

back in a day NES and PS1, i only have less than 20. my PS3 and Wii library increased a lot last year and this year(probably around 20+). for PS4 and Wii U, i've got around 20 and ~30 each. 3Ds - got around 15+

Usually 30s - 40s games per console from 6th to 8th gen.

From 3rd to 5th gen is about hundreds.

Depends on the generation and my life circumstances.

NES I had 30+ (grade school)
SNES through GC I had less than 10 (HS and college)
Wii, PS3, WiiU 30+ (professional)

From here on out, I could see it staying at 30+.

Around 30 - 50 on home consoles. Around 1 - 10 on handhelds. The only exception is the Wii where i had over 70 games at one point. maybe even 80.

Around 20 games

I'd say 4-6 games a year so 20-30 range for most systems. Hard to say now as share a library with my husband.

12-20 counting also my old consoles 

Usually about 30 games but for 360 it exceeded 180 :).