For me it's: BOND 007 NIGHTFIRE.
Little Big Planet 2 (and 1st).
Endless amount of levels to play and you could create your own as well. So many different levels and I met so many nice people that I used to play with everyday. A lot of good memories from that game. Amazing game and suited perfectly for when I was around 9-12 year old
Idk which one would be the best but judging by impressions left after finishing them my top 3 is Tes Oblivion, Witcher 3, NFS Most wanted(original one not 2012), although oblivion and tes mw were my childhood games so maybe they were not as great as I remember them, Witcher is an absolute masterpiece tho, I have 240 hours and I gonna rerun it with next gen for sure. Honourable mentions: metro exodus, fallout nv and stalker series, metro has insane graphics and atmosphere, new vegas was a breathe of fresh air after trash fallout 3, and stalker is just stalker.