In terms of number of games played I have to say nothing beats the HD4850 amongst all the cards I owned.
Most to least favorite:
1. Triplex HD4850 512mb GDDR4
2. Sparkle Geforce 2 MX400 64mb SDR - finished Doom 3 with this card, I couldn't recall how.
3. Palit HD4670 Super Ed. 512mb GDDR3
4. XFX DD HD7950 3GB GDDR5
5. HIS IceQ X Turbo HD6870 1GB GDDR5
6. Sapphire Dual-X R9-270 2GB GDDR5
7. Sapphire Vapor-X Tri-X R9-280x 3GB GDDR5 x2 - originally intended as a mining card, got to play with it but this was during the non-gaming days of my life so I never got to play with even above casual hence the lower rank.
8. Inno3d Green Ed. GTX 750 1GB GDDR5 - good clocker, but it only lasted in my hands for few months, card was overkill for my needs.
9. EVGA GTX 460 FPB 1GB GDDR5 - died after a month, got it back from RMA 5mos. after, got to play with it for a few months till I got rid of it
10. Powercolor HD5750 1GB GDDR5 - got it 2nd hand, poor clocker but got the job done for a few months
11. Inno3d 7600GST 256mb GDDR3 - started manifesting issues after the first 6mos. had to underclock it to keep it stable
12. Asus 9550 256mb DDR - got it for few days, gave it to my bro. ( psu issue)
13. Sparkle Geforce 4 MX 4000 128mb DDR - no memory of this card aside from the fact that I use to have one before