I'll rank them in order of importance to the video game industry. I'm only listening franchises, so no Pong.
1. Pac-Man (Really kick-started the industry and brought in females)
2. Super Mario (Saved the industry after the video game crash)
3. Pokemon (Has kept handheld gaming relevant, nothing has been comparable to "Pokemania")
4. Tetris (Kick-started handheld gaming)
5. Grand Theft Auto (Popularized open world games)
6. The Legend of Zelda (Basically created/popularized the action/adventure genre)
7. Doom (Popularized the first person shooter genre)
8. Metal Gear (Popularized stealth gameplay and movie-esque storytelling)
9. World of Warcraft (Largest MMO of all-time, brought MMOs to the mainstream)
10. Angry Birds (Kick-started phone/tablet gaming)
Honorable mentions...
Halo (Popularized online console gaming)
Call of Duty (Reinvented online FPS games)
Final Fantasy (Popularized RPGs in the west)
"On my business card I am a corporate president. In my mind I am a game developer. But in my heart I am a gamer." - Satoru Iwata
