I used to do that, back when I could get a game for £20 for the PS1 or PS2, and there were bargain bins with actually good games in it, and I didn't really have to buy them myself.
I have picked Armoured Core, Mass Effect, Freedom Fighters, Jade Cocoon, Medieval, Rome: Total War, anything that was 40k (I remember the hype when Dawn of War released, christ).
But I agree with Cannibal Corpses above; today, when companies are willing to ship terrible pieces of shit for full £60 prices with unimaginative gameplay... I can't afford to waste money anymore.
Also, I don't have the time to game willy-nilly either; if I want to play a game, I have to REALLY want it, because I have bills and such to pay, holidays and anniversaries to save up for and so on.
So I can only buy games I KNOW I can trust buying, I have heard it's good and I am interested... and usually when it's price has dropped. Frankly, video games as far as value goes has significantly dropped in my mind.
I used to play Dawn of War or Civilization 2 or Super Mario Bros. for hundred of hours, and now? I'm lucky if a game offers more than 10 hours of gameplay.
Even the best games this generation like Skyrim? Bland, artificially lengthened, samey, copy-pasted quests, big but full of nothing boring story, what a waste. However, I admit I have high hopes for MGSV and FFXV (that summon demo).