It's probably the most intellectual first-person shooter out there.
Its better than some, but I wouldnt say that. Half-Life has puzzles and such in and an interesting plot, and Planetside forces you to think about team actions, you can still go it alone in TF2.
Half-Life 1 and 2 are just mow through zombies and we'll throw plot twists at you. TF2 has a lot of not only team thinking, but fast thinking to gain the upper hand in 1 on 1 scenarios. For instance I play soldier so I'm always looking to get higher ground so my rockets have a better chance of hitting, whether that will entail running up a staircase, rocket jumping into the air, or any other way I can find.