With some effort, MM, QC and SPLT can get you a lot of EXP in very little time. (~1000-2000 depending on kills/floor covered/role)
PvP games such as TH, T/SW, T/HG and OITC can get you a lot of EXP, but only if you're able to get a lot of kills (like, at least 5. can get 300-400 EXP, I believe...