I started to beat shoot 'em up's on C64 without using trainers. The first one was Nemesis (aka Gradius)
I recall I was waiting for more stages and bosses but it just started again from the beginning and I was blinking at the TV screen, wow, I did it.
Manic Mansion was game that introduced me to adventure genre. A lot has been said about this game in various places, it was huge back in the day. I still prefer humour or even surrealism in my adventure games, though I liked Cognition: an Erica Reed thriller too.
Miroprose's Gunship introduced me to simulators, then somewhere along the way they became too complicated.
Roadwar 2000 and Roadwar Europe were sort of light strategy games I liked a lot. I guess that's why I still like light strategy games like nu XCOM. Original UFO: Enemy Unknown was something else though.
Pool of Radiance introduced me to cRPG's. Then Baldur's Gate and Might and Magic series I ended so overdosed of fantasy that I can only tolerate Arcanum at these days, because of Steam Punk and Shadowrun because of Cyber Punk. Fallout, well that was something different.
Doom and Dark Forces are sources for my disappointment with modern shooters.
Mass Effect series, aka dark comedy about how to fuck up a franchise and screw your customers. First in the series, all wasted potential in the sequels. Perhaps it would be good time to abandon fantasy and sci-fi and try something new with urban fantasy or something. So there are protagonist John, James and Juliet in the beginning of something that may turn out to be Zombie apocalypse. So John works in a store, he has skills with people and is decent with throwing weapons because of hobby. He has low staying power though. James drives a garbage truck. He is terrible with people but when you need ride trough those Zombies with a lorry or something you need him. He is also good with hand to hand combat and shotguns. Juliet is a nurse, she is outspoken but rarely says anything of value, useful in certain situations, but then it turns out that she can't actually treat anyone, actually she couldn't work as nurse because it just wasn't what she imagined, but still likes to bring her education up because everybody likes nurses right? And she failed because of daddy issues and at that point you can shoot her in the face or sell her to brothel or something and take your chances to find someone actually useful.