I had a C64 as a kid. It was the next gaming machine I received after having the 2600 beforehand.
I'll be honest when I say, I was never a fan of it really. I realise this is a thread dedicated to the opposite sentiments, but, although I never outright hated my C64, I couldn't wait to move on from it tbh.
However, I did enjoy the Cartridge titles that came out for the machine. I had a lot of those as my Mum bought me a load to go with the machine: Shadow of the Beast, Robocop 2 & 3, Chase HQ 2, Navy Seals, Batman, Pang, Space Gun, T2, Toki and that 4-in1 cart that came with my C64, which included the rather excellent Flimbo's Quest.
Outside of the Carts though, I was rarely impressed. Of the one's that did grab me, I enjoyed the Turrican series, Midnight Resistance, Catalypse, Cosmic Causeway & Trailblazer, Cauldron 2, Last Ninja series, Cyberdyne Warrior. probably some others.
Overall though, I couldn't wait to get rid and grab an SMS or NES instead.