Let's see...
-Sega-
It doesn't look like Sega's support is bad at a glance, but, well, their titles haven't seemed to review well. Still, at least they made an attempt...
I own six of these which are the two House of the Dead games, MadWorld, The Conduit, Sonic and the Secret Rings, and Mario and Sonic at the Olympic Games.
I'm interested in trying the other Sonic games, Samba De Amigo, and Nights, and am definitely getting Mario and Sonic at the Winter Olympics at some point.
-Konami-
What's Deca Sports doing there? I thought that was Hudson.
I own just one of those, Elebits, which I really enjoyed. I'm interesting in trying Dewey's Adventure and Silent Hill, and that's about it.
-Take Two-
I have none of these, and the only one which I want to try is Bully. I played Carnival Games and liked it, but since my friend has it I feel no need to buy it myself.
-Namco-
I have none of these either, but want to try a few. I guess Nintendo published Mario Super Sluggers and not Namco?