Personally, I think the GameCube has been the best. I'm probably alone in that opinion, but was proportionately less bad games than other systems of the time. Load time was fast, great graphics, and a stellar lineup of the first titles. My favorite system is however the Sega Genesis. This is really more for nostalgic reasons.
Personally, my favorite game system is the Game Boy Micro. It is the perfect gameplay and ultra-portable. Plays all Game Boy Advance. It has a backlit display, headphone jack and all buttons Boy Advance game. It's all packed in a gadget smaller than my cell phone. I put it on a lanyard and wear around my neck at times. It also fits well with its jacket pocket or any other stock of portable electronic devices. It is almost indestructible. I've had mine since it first came out Micro in the market and still looks almost like new. I got a screen protective film on it. A little over a year, I found a silicone sleeve to put over the rest of it. Leave the buttons and game port free, but the smooth surface makes the system easier to hold. It could also help protect from bumps and drops, too. I left mine more times than I can remember and is in great shape. The battery is rechargeable and is kept within the system. I have one of those car chargers to charge Micro, Game Boy Advance, Advance SP and Lite. Works great I can charge my Micro, Advance (yes, they still have a very old Game Boy Advance that allows children play with their parents and when they come visit) and DS all with the same charger. You can replace the face plate with different looking like you can with a phone cell so you can tell your Micro someone else. Hard'y You see them around anymore for some reason. I do not know if people lost theirs or if they stopped aside in favor of the DS or PSP. I like my DS Lite as well (the touch screen is fine), but I still take my trusty Micro when I play but not want to take A case of large game. The Micro is probably one of the most underrated and overlooked game system out there. Sure, it's still a Game Boy Advance but that's what I think the Game Boy Advance was meant to be, for starters. I used to have a Gamecube too. What I like about it was the adapter I got for it, so I could play Game Boy Advance games are using to play on my TV with my Gamecube controller. I switched on my Gamecube, among other things, a Xbox 360 after playing games on it with my friends. The Gamecube system was little, especially for children, but most games I really wanted to play is out of the 360 in place. My favorite games were Nintendo GameCube Star Wars Bounty Hunter (finally got to see what it's like being a guy like Fett Boba Fett / Jango one of the best Star Wars ever.) Samauri Jack (I heard it's a version for Xbox and I want to find) and Metroid Prime (Metroid I pretty much sucked, but the graphics Gamecube was shown capable of more than cynical given credit for.) I played the original Sonic the Hedgehog Genesis game on the friends of the house of one when I was in college. Even play the Game Boy Advance port of the same and the version of DS (Rush Sonic). It could have been a geat as many followers as the Playstation One or more if Sega had better options.