Tough call between Age of Franchise and Halo Franchise. While I played both extensively in the early days, the latter days have not been so kind to both franchises.
I will take it easy on myself since I want to go to sleep and just choose based on my top 50 list.
15: Age of Mythology PC
7: Halo 2 Xbox
Looks like Halo wins based on how much fun couch Co-op and 4 player LANs were. Still these 2 are my top rated RTS and FPS respectively, with none yet to topple it.