As far as home consoles go, there are a lot of favorite for me, with top three being Nintendo 64, GameCube, and Xbox 360.
Nintendo 64--this one had given me millions of great memories. Used to play games on it nearly every day as a kid (whether it be with friends or alone), and have enjoyed each and every second. There were plenty of titles available for it, too. GameCube, same story, but in some way, it was even better. Its graphics were higher of quality, for most part, and its controller was also easier to handle, as it had less bulk. Also, button layout was nice; it made clicking much easier. Xbox, I've personally found its online features to be pretty outstanding.
For handhelds, 3DS ranks above all at the moment. Well, at least for me. Although I haven't gotten any chance to try much of its games out, ones I did play were able to keep me entertained pretty well. So far, from all the ones I've played, my favorites have got to be Super Mario 3D Land, Legend of Zelda: Ocarina of Time, and Mario Kart. They've been released some time ago, but regardless of how much I play, these games just never seem to get boring, thankfully.