I agrtee with Night striker. While that is alot of singstars they cater to different people. Personally my vote goes to Guitar Hero. I think i read somewhere that theres like 5 of them coming out this year. Talk about milking

The Mario IP is certainly being milked(though not to the point that it will have a negative effect on sales).
This is thanks to the fact that the IP has spawned 5 not-so-milked franchises:
Platformer
RPG
Sports/Racing
Party
Puzzle

Of which I'd certainly call the Party series milked during it's time, though it's probably due for a proper update after WM+ is released.

Sonic, NFS and mario.

oh yea NFS.. its been around for what over 12 yrs and a new one keeps popping up annually

I'm not sure I'd count something like Singstar. Being music orientated is lends itself to a continual stream of updates. I know these are being released individually but I see this in the same manner as the constant stream of new music for Rockstar, etc.

There's no milking going on because its the same title really.

Milking IMHO requires lots of differing, increasingly crazy spin offs and the wearing thin of an originally focused concept.

I googled this up..

http://www.smbhq.com/list.htm

its a list of all games of Mario or has a cameo of him up to the Gamecube Gen (Does not include Wii or NDS) ..i think overall Mario has been milked more due to the accessibility of obtaining most of the Mario games worldwide (we've almost all of the Mario games in stores), whereas there's only a handful of Singstar games that are even in NA.