I'm going to be controversial here and say Portal is not the best single-player game out on PC at the moment. It's a great game, true, and ranks as one of the best, but it's not the best. Best is just a matter of opinion, after all, but there are plenty of single-player PC games older than that which are more worthy of the title. For example, The Longest Journey was a landmark game for the adventure genre, taking the best of things like Broken Sword and some of the earlier Lucasarts games (before they went Star Wars crazy and stopped making creative, innovative games like the stuff Tim Schafer does and did), and then added to all that with a much more compelling and well-written storyline, realistic and likeable characters (the best case I've ever seen of well written characters, in fact, and years before Half Life 2 came along with Alyx Vance and Dr Breen...), and overall a much better feel.
So yes, though Portal is great, it's nowhere near the 'best'. There are other titles out there that are much better. And besides, 'cake is a lie' jokes are just silly and old now. And though Still Alive is good, Jonathan Coulter has done more than just that, you know...
