Definitely NES, by far the system with the largest amount of good games and the largest amount of great games. Still my most-played system and I can't see that changing.

1. NES
2. SNES
3. Genesis (close to #2)

N64 because it had the banjo kazooie games, the best legend of zelda games, the pokemon stadium games, pokemon snap, and donkey kong 64

1. PS2 It had so many games that I loved and also when I own now a Wii and a PS3 I still play the most of my time with the PS2 incredible.

2 and 3. Difficult I am stuck between Snes and PS One. Both have a huge library with games that I love so much. Example: Snes FFVI Awesome! PS One FFIX awesome.
Snes: MK!! PS One: CTR! Snes: Killer Instinct! PS One: Tekken! Snes: Mario! PS One Crash bandicoot! And I could go on...

4 Nes
5 DreamCast or Genesis.

GC *gets hit by tomatoes* because it had the best games, Mario Kart, Wind Waker, Mario Kart, Mario Sunshine *gets hit by more tomatoes* Mario Kart, Super Smash, Mario Kart, Mario Party *gets hit by MORE tomatoes* & most importaintly Mario Kart.

Neo Geo, Kofs, Samurai Shodowns, Real Bouts, Last Blades, Metal Slugs, Magical Drops, Bust a move, Blazing Star, Pulstar, Andro Dunos, Sengoku 3 (the best non 4+ player beat em up), Shock Troopers, and a hand full of other fantastic games make the neo geo my favorite system, plus no loading, perfect controllers, or odd ball problems or cuts make them the best version.
Granted many of these games can be found on other sources but nothing tops playing them the way they were meant to be played, plus Sengoku 3 will probably stay a neo geo exclusive though it's a shame considering how good the game is,
Second is the saturn, Shining Force 3 and Panzer Dragoon Saga are the best Strategy Rpg and Rpg in existence in my opinion, plus other games I enjoy so much like NiGHTS, Beyond Oasis, Deep Fear, Radiant Silvergun, Die Hard Arcade, Darius Gaiden, many capcom fighters, sega's ports, the better version of Symphony of the Night (maria, running, the new areas and power up more than make up for a few odd ball instances of slowdown and special effects), Megaman 8 (woodman and cutman), Dragon Force, Guardian Heroes, and more, the saturn was what I wanted in a console.
then the genesis, I just like Sonics, Shining Forces, Phantasy Stars, Shinobi 3 and so forth more than what the snes (square rpgs do nothing for me, I can't stand them, but I can understand why people like them) had to offer
Overall my ranking would be
Neo Geo-Saturn-Genesis-Nes-Gamecube-Vectrex (exclusive supplier of vector graphic, I *HEART* vector graphics, plus I likes about half of all original vectrex games and homebrew rocks!)- Snes-n64-dreamcast-Atari 2600-turbo grafx 16-intellivision-ps2-ps1-atari 5200 (would be higher if comp pro's or wico commands were stock but they aren't)-Jaguar-3do-atari 7800-xbox-colecovision-odyssey^2-Fair Child Channel F-Bally Astrocade-Emerson Arcadia--thus ends my report on my preference on good systems (those with at least a few games I enjoy)
order for "bad systems"
-Cd-i-Memorex Vis... and the bottom of the barrel of the systems I've ever played is..... (drum roll)
THE RCA STUDIO 2, if you say any system is worse than this piece of work you are just plain wrong, this isn't a matter of opinion this things crumbiness is a matter of fact, nothing is worse than this, 1 no color B&W only, 2 sound is limited to a buzzer 3, the controller is a keypad built onto the face of the system complete with difficult to push buttons, 4 in terms of processing power stacking it against the 2600 was like comparing a 2600 to an xbox 360 or ps3, 5, the games are all compete trash, first the controller renders them difficult to place then the games themselves are all terrible, oh and one of the headlines on the box is a game called "pattern", which just displays static
and the really kicker is rca denies the existence of this folly, that right the creator of the studio 2 insists it never existed,
well that about covers every system I've ever tried out
handhelds
ds-gba-original gb-psp-Neo Geo pocket (I'm sorry old friend you've been edged out)-Microvision-gbc-gamegear-lynx-Watara Super Vision----------------------------------------------------------------------------------------------------------------------Game.com
and that covers the handhelds I've played

It's a tie between the PS2 and SNES.

Dream cast

it was definitely a unique console with unique games
a true gamer console
it had phantasy star, skies of Arcadia, and power stone 3 of my favorite games

XBox 360 a lot of great games released in a short time , many more great games to be released and it has over 300 games available in its library.

Best: SNES. So many origins, revolutions and legends.

SNES undoubtedly. Earthbound is my favorite game forever!!