I've played:
Banjo-Kazooie - Great, well-balanced, long, fun. Awesome. Beats SM64. 10/10. My pick.
Banjo-Tooie - Adds way too much and as a result becomes extremely boring. Big mess-up here. 6/10.
Conker's Bad Fur Day - Good, some interesting ideas, but clunky control and some incredibly annoying/difficult parts. 8/10.
Diddy Kong Racing - Great, best racer on the N64 I've played. Multiple vehicles, great tracks and awesome adventure mode ftw. 9/10.
Donkey Kong 64 - Oh dear. Take Banjo-Tooie, replace the characters with DK characters and add EVEN MORE and you get this. Sorry, but I got every single thing the first time I played it, and now every time I try to play it again I can't even get past the tutorial barrels at the start before getting bored. 4/10.
GoldenEye 007 - My favourite FPS of all time. Extremely addictive, great multi, you'll want to beat every mission on every difficulty in single player and unlock all cheats (I did). 10/10.
Perfect Dark - Good, but the main game is relatively boring compared to GoldenEye IMO. Multi's great just like GE. 8/10.
Haven't played these:
Blast Corps
Jet Force Gemini
Killer Instinct Gold
Mickey's Speedway USA |