Franchises you wouldn't mind being milked...

KOF
Street Fighter
Phantasy Star
Gradius
R-Type
Contra
Metal Slug

I would not mind if they make a new Metal Slug game every 2 months.

Rez
Soul Calibur
Samurai Showdown
Panzer Dragoon
Street Fighter
Burning Rangers (does anyone else like this game?!?)

... and some others

Sonic (2D, 3D, anything)
Jet Set Radio
Klonoa
Wonder Boy
Alex Kidd
Shinobi
Shining Force
Dark Cloud
Lunar
Golden Sun
Metal Slug
Mr Driller
Fantasy Zone

For the sake of simplicity I didn't include games which are not "series" yet.

Let me add Wonderboy and Advance Wars to my list as well.

Beatmania IIDX - Just add some new songs and I'm set.

Any other "music" game I enjoy - See above

Metal Slug - Keep it 2D and I'm happy

Dynasty Warriors - Just add a character or two, maybe some new moves and environments and I'll be content.

There are likely more but I'm too lazy to list them....

Actually, I am a little sick of them milking Dynasty Warriors, they really need to do something new for DW 5, or else it'll be the same as DW 3 and 4 with minor improvements.

Soul Reaver- I could never get too much of this series

Tomb Raider- If they were like part 1 instead of how they killed the franchise I could use more of these too.

Mario

Zelda

Gunvalkyrie, even though there's no chance that would ever happen.

Art of Fighting
Bust-A-Move
Castlevania
Contra
Darius
Darkstalkers
Daytona
Devil May Cry
Dino Crisis
Fatal Fury
Final Fantasy Tactics
Final Fight
Ghouls 'n' Ghosts
Golden Axe
Gradius
Grandia
House of the Dead
King of Fighters
Klonoa
Lunar
Mario
Metal Gear
Metal Slug
Onimusha
Phantasy Star
R-Type
Resident Evil
Salamander
Samurai Shodown
Sega Rally
Sengoku
Shining
Shinobi
Silent Hill
Sonic
Splatterhouse
Star Fox
Street Fighter
Streets of Rage
Suikoden
Teenage Mutant Ninja Turtles
ThunderForce
Vandal Hearts
Virtua Cop
Virtua Fighter

Keep 'em coming.

I also wish Konami would make some more 2D Goonies games for the Gameboy Advance! :D