The times below are how long to complete it after days/weeks/months/years of practice:
Another World - 1 hour
Flashback - 3 hours (in one go)
Hunter (all 3 sections - I did save in between each though) - unknown time, several hours at least
Lotus Esprit Turbo Challenge - 2 hours (hard level), 270 pts
Mega-lo-mania - 3 hours
Santa's Xmas Caper - 30 mins
Speedball 2 (knockout and league) - 1 hour for knockout champion and 2 hours for league champ (all games undefeated
Super Cars 2 - 1 hour
Many more I can't remember...