I found RFoM alot more fun then CoD4, it has a better story, 40player online compared to 18players in CoD4. The online in RFoM is lag free even with 40 players all tossing hedgehog grenades in a room at each other, while CoD4 lags with as little as 6players in a game. Try to play Bog with 18players and the game lags like crazy and the FPS drop to single digit.
CoD4 has no clans, no typed messages, RFoM has separate squads in online games, which is amazing. CoD4 also has no gameslist.