In order of preference it goes like this...
The Guild - I really want play more stuff in this genre, I'm a noob at these sort of games and it's time I fixed that
Deus Ex - I've played the 2nd and 3rd games but never the 'big one', embarrassingly
Caesar 3 - Love the setting, I think I could really get into it
Gabriel Knight 2 - Haven't played many adventure games outside of the ubiquitous Monkey Island and Sam and Max series, and this is a classic that still looks good today.