Given that I haven't seen a recommendation up for his games yet, I'm going to shill for Goblinboy's AIF games. I'm sure those of you that frequent SL will be familiar with them, but for those who aren't, here it is. AIF are adult interactive fiction games, typically text-based games similar in function to the MUD predecessors of MMORPG games like Everquest and WoW. These games are very often linear, with a series of quests or actions that the player must go through to romance or get the girl/girls, at which point there is a text-based interaction.
Most of these are strictly text-based, with pictures being limited to an extreme few games. To my knowledge, only one author has bothered to develop a full gallery of pictures for the interactions (and otherwise) in his games, and that's Goblinboy, even going so far as to recruit someone to help with the coding. That's a point to note, if you download the little TADS engine to play these games, there's really not much point in trying to find games of similar quality in the same engine - they don't exist.http://www.tads.org/
I'd include links (there are also very completely walkthroughs), but they generally go back to the Shark's Lagoon forum, so look it up if you're interested.
Games by Goblinboy
: (There are more, but I'm only including his highest quality graphical games)
Gift of Phallius 3
Tesliss Equation (new as of Christmas)
The latest is somewhat more linear than the others, and it's my understanding that the author is taking a break from development, but I've enjoyed it so far. The contents can be squicky depending on your personal tastes, as there is a thread of inc in the get-all-the-girls to complete the harem style that it offers. Still, there are plenty of alternatives, and multiple endings to cater to however you played the game.