Well, Foolycooly mentioned all the cases popular with gamers and JayE2992 added another popular case. Pick the one you like that meets your requirements.
I haven't seen actual sales figures but from what I have read I am willing to bet the Antec 900 is probably the most popular case with gamers.
My personal case is a CoolerMaster HAF 932. It's huge. Ventilation, airflow, and cooling are excllent. Cable management is terrific. It is designed for a variety of configurations. Very flexible indeed.