Summoner was a really boring game that I finished only because I have no life. The graphics were great though, especially if you have them pumped up and with FSAA. There's a multiplayer for it, but it's lame, so I don't know why anyone would do it, even if free.
Vampire is ok, if you don't expect too much from it. It could be cool if you know the right people.
Baldur's Gate 2 is good, but that's a big jump up from diablo.
Check out
www.theunderdogs.org for some old but goody single players though.