Which video game franchises are most consistently good, and which least consistent?

Really depends on your preference.

if you're looking for a great RPG then I suggest the whole Elderscrolls franchise as well as Fallout franchise.(PC,XBOX360,PS3)

If it's MMO's the Diablo franchise is great as well.(PC)

Call of duty has a few good titles for xbox and ps3 obviously.

assassin's creed maid series (AC1,AC2,AC3) is quite a great one too as well as on all titles.

Borderlands 1&2 is quite decent (PC,XBOX360,PS3)

Halo 1,2,3,4 (xbox 360)

and most sports games.

NOW for least consistent it's hard to say,most franchises all have their ups and downs if they didn't it wouldn't be much of a franchise if it had only downs.

Gears 2 was a disappointment in my eyes so I guess it's a little sad.

Skate games were pretty average too.

if you're looking to kill **** i'd really go for battlefield (for looking for skill) or Cod just to have a little fun.

if sports Fifa has a great franchise so does NFL,NHL.

the MLB was a pretty shitty franchise if I might add.

Animal Crossing :)

half life, halo, uncharted, borderlands, gta, batman arkham, mass effect, sims