Obviously there are dozens of options for each category, but I'll choose some examples. I will list no adventure games, as I have completed most of what I have (dozens).
1. Which Amiga Games were impossible to complete without cheats ?(ultra, mega, very difficult, etc)
Shadow of the Beast 2 (The first one was a piece of cake compared to 2! I couldn't even complete it WITH
2. Which Amiga Games did you almost complete (almost, but not to the end...)
Rodland (couldn't beat the final boss no matter how many lives I had)
3. Do you want to complete any amiga games in near future?? (on emu or real amiga)
All of them! But that would never happen..