I'll base it off the game I used to like and play - since now all I like is Pokemon; by now my younger brother owns the system, or sold to friends, not actively seeking them anymore.
My favorite games by systems I played - not counting the Pokemon games
• SNES: "Bubsy: In Claws Encounters of the Furred Kind" don't know why exactly is my #1 favorite from the SNES, but it was the first fun game that both my grandma and I played, especially when I was young -about 7 to 8 years old- strong memories of that game
• Sega Dreamcast: "Resident Evil: Code Veronica" (I believe that was the game) was a console that my uncle own for about a year and half, and it was the only game he had for it, It was fun playing the game.
• N64 - "Conker's Bad Fur Day", it was the the one game I could spend hours and always had fun, and with 2 to 4 players my entire younger brothers could join in the action. Kind of graphic and so much bad language, it was still too fun to let it down.
• PS1: "Driver 2" not as fun as Conker... above, but it brought me hours of fun
• PS2: "Grand Theft Auto: San Andreas" - "Grand Theft Auto III" & "Grand Theft Auto: Vice City" - I was a big fan of the GTA series, those 3 where my favorites of them all, especially S.A.
• PS3: "Grand Theft Auto IV" still play it occasionally, when I first bought it (a few weeks after its release) I couldn't let it down, it was hours of fun, just messing around
• PC: "Sim City 4" no other simulation game comes close, the new one is even worse (everything fun from SC4 was removed), I still play it at least once a week, love designing a wide variety of scenery and metropolis
today all I own is the original Nintendo DS (the grey colored console), Nintendo DS Lite, and Nintendo 3DS XL - my younger brothers and uncle have bought games they like for the DS/3DS I'm only sticking with Pokemon games as they are the only ones that bring me joy and hours of entertainment. All of the games I used to like (mentioned above) I can play them for about 15 to 30 minutes and slowly start getting bored.