I could help but the term 'Popular games' is to vague the most popular game in the world , known as world of warcraft only requires 64mb Grphx card, yet the extremely popular Battlefield 2142 requires alot more power than that. Or middle games like Call of duty 2 run quiet well online with average components
im running CoD2 on the following (i am soon upgrading)
Athlon 2500
Radeon 9600xt
25GB 2mb cache HDD
1GB Budget Ram
Creative Live 24-bit audio.
Very Old motherboard.
Please be more specific and i will gladly help, in a perfect situation you could helpfully list the games you will be looking to play.
Thanks