Is it possible to easily collate recommended system requirements for all owned Steam games?
Solution 1:
You can individually go through and look at the stats and comprise a list. Also, I think there is a website called canirunit.com in which you can type in the name of the game and you can get recommended specifications there.
Solution 2:
I know it's not exactly what you want, but you can have a look at the Steam Hardware & Software Surveys to gauge what other people are running on their PCs. You can use this as a rough guide for what works and what doesn't.
For example, the average Intel CPU speed is 2.3-2.69 GHz, with 49% of people running dual cores, 43% Quad core.
As for RAM, most seem to be running 8GB however over December there was a trend up of 2 and 4 GB machines (probably as people got laptops for Christmas).
Like I said, it's only a rough estimate of what other people are running, but if you stick to the averages (or just slightly better than average) you should be able to get a reasonable laptop for most games that you play.