Portal has to be one of the most unique, fun and challenging games I have ever played! It's worth the money alone.
I unfortunately am not a live gamer so I haven't had the pleasure of playing team fortress... But I have heard good things from a group of friends who have been obsessed with its game play and online play.
(If I miss interpreted half-life wrong forgive me I only played it for a few hours.)
Half-life I think is a bit over rated. The story has potential. With the concept of the Government with such power and a form military/police state With people trying to get out of the cities and such it keeps you paying attention.The graphics for the game are very well done. I consider the look to be eye candy. As for the actual game.... not so much. It has you running around without a very clear direction. The health system was horrible. You either ran out to quickly or you couldn't find enough health. The guns were slow at first which frustrated me to no end, and about time I finally got a faster weapon I was so tired of the game I shut it off. The enemies weren't hard to kill but they were everywhere! to a point that you just wanted to run through the game instead of playing it. Lastly on the subject of running I found it hard to even do that. With barrels and crates all over the canal they constantly got in the way causing you to get shot at more than necessary.
Moving on to the real reason why I bought the game... Portal.
Portal is very unique. Your trapped in this creepy sort of abandoned testing building with a equally creepy AI testing robot voice following you around. The game may be a puzzle game but with the portal concept that's all that is needed to cement your addiction to this 2 hour long game. The puzzles need a variety of ways to use the portals to solve which keeps you coming back to skills you previously learned making you feel progression constantly. The portal concept is amazing and hard to describe. Going through a portal to the other side of the room or another area is such a neat concept! You may find your self stopping at a spot, shooting a orange portal at the ceiling, and a blue one at the ground right underneath it and jumping through only to be seemingly stuck falling through portals! The only real problem I had with the game was the number of tests at the beginning and test #18 which I had to learn to glitch by... but for the most part I enjoyed the game... even enough to beat it twice in one day.
Truly though my words can't really do justice to portal because to me it's kind of hard to describe... its new, funny, challenges you and rewarding. Half-life would be a great game if the game play wasn't so hard because the story did catch my attention.... and as for team fortress I am unfortunate to not played yet but sounds good!