Shocking, isn't it?
Seriously get HL2, it's the best game I've ever played.

On a related note: what are your thoughts on Steam? I really don't see what all the fuss is about. It's user friendly and it stops piracy pretty much dead.
Critics are a good source, but not the authoritative word on everything. Perhaps a better reason for piracy is that unless games were lower priced, you wouldn't buy a certain game. Perhaps it looks good, just not 50 dollars good. Playing the game is the only real way to find out if you'll like it or not. If you decide you do like it, then you'll know the critics aren't full of crap and that you'll probably enjoy similar games. Perhaps a better comparison would be a guy with an ice cream shop. He has dozens of different flavors, and you ask to sample each one. Some you like, some you don't, but you'll likely buy more a bit later when you aren't full of ice cream samples than just sticking with safe old mint chocolate chip.
I don't really get this.

The people who invest a lot of money, hard work, and passion into a product, want you to contribute. They don't want you to speculate about paying a totally different company for a similar item somewhere down the line. 'Thanks, you're right, that apple was great dude, but I really can't be bothered to pay you right now... seeing as you don't have any more, maybe in future I'll buy some similar looking apples from some other guys, how's that?'.

The whole thing about games is that by the time you've played it to find out if you want to buy it, you don't need to buy it any more. I really don't think that this is a tenable position.

Using reviews and playing demos is totally sufficient for finding out if it's a quality game you'd like to play the rest of. You don't need to play the entire game to work out if you want it.