polishedness. the guns act, sound and feel realistic. the multiplayer side to COD4 is polished to perfection. the ranking system is addictive. the weapons and perks work greatly. It really out-does rainbow six:vegas in every way. Infact vegas 2 is trying to do what COD4 is doing already, even before release. COD4 doesnt over-glamorise warfare. It brings it to you. the sniper mission in chernobyl is amazing. I've never played anything so atmospheric and cinematic (in a certain part).
But COD4 is all about the multiplayer. Its inexplainable in a way. Its the online game you always go back to. To rank up a little bit more. To get more upgrades. To play that map you love again. To try a different weapon/perk combo. Its brilliant. I think you havent played it enough to realise its greatness yet..
a very important thing to say is this though.. COD4 is just as good on PS3 as it is on PC. Infact the PS3 version is better than the 360 version technically. And parts of the online mode are done better than the PC version (prestige mode, server connecting etc). If you're saying that aiming and sniping is bad on the PS3 you just havent played it enough yet. I sit infront of my TV and my hands are working magic on the sixaxis when playing COD4. Once you master it, it works great. Infact I enjoy it more than on PC in some ways. All your criticisms of it so far seem to be due to not playing it enough. I can understand your doubts but seriously. Spend a week playing it