Do You Collect Games to PLAY or PUT on the SHELF?

Does SHELF APPEAL factor into any of your game purchases, or do you stick to only games you plan on playing?
Example: say you stumble across a bunch of mediocre or outright awful NES/cartridge games that you don’t have in your collection, but they’re priced dirt cheap. Do you buy ’em up, thinking that expanding your NES collection would look that much more awesome on display? – Eric Hubers