The Genesis slot was the tightest for sure. Pulling the games out from the side seems to be the trick. Also, the NES one felt like it was scraping the shit out of the contacts. The GB slot is super smooth though, wish they were all like that.
http://blog.us.playstation.com/2011/07/26/psn-and-thq-50-off-content-sale/
http://blog.us.playstation.com/2011/07/26/fat-princess-big-ole-anniversary-bundle-sale/
Not sure if those were posted already.