Portal 2 the greatest Valve game ever? I loved Portal but I think that combined HL2 and E1 & E2 represent Valve's best efforts to date and I don't see Portal 2 changing that but we'll know this fall. However I would suspect what's next in the HL series will be another hallmark.
My statement was based on the observation that every single game Valve releases is an improvement on what they did before. Each HL2 episode was better than the last. The new L4D2 campaign has IMO among the best map design and coolest environments of any game they've made so far. It will not surprise me if their next full length single player game, in this case Portal 2, represents the best of their single player game design experience.
One thing is certain, Portal 2 won't motivate me or anyone else to buy $1500 worth of GPUs. Not a knock on the game just simply a fact, I'm looking forward to it as well.
The kind of person that buys $1500 worth of GPUs is also statistically irrelevant. Look at the number of people on the Steam hardware survey using GPUs anywhere close to that price range and tell me that it matters. It may be an aspirational benchmark but it is also a negative benefit to developers when your game doesn't scale well and only looks good on very expensive systems.
Anyway, congrats on taking yet another thread way off-topic once again.