My buddies and I started playing p&p RPGs in the 80s and kept on playing until the mid-90s, from then on it became increasingly difficult to get a group together. Most of the time I was the master, good fun. We started with the simple stuff like DSA, (A)D&D, Midgard and MERP, then switched to Rolemaster and it became our RPG system of choice, even though it's a bit complicated compared to most other systems, getting character development and levelling-up done takes ages without a computer program. Back in the day we used a REXX script on Amiga that did most of the calculations but it was very slow and buggy. Other faves of mine were/are Call of Cthulhu, Paranoia and Warhammer.
Still have all my RPG stuff, it takes up half a shelf in my study. One of the guys who used to be in my group started playing again a few months ago, sadly they quickly changed from p&p to real-life roleplaying, I'm not a fan of that tbh, running around with wooden swords and DIY armors isn't my cup of tea. I got several offers to sell my RPG stuff, there are people who pay top money for original first/second-edition Rolemaster/I.C.E. rulebooks and companions in good condition. Not going to bite, though, someday I will give the stuff away for free to a RPG club or something, these games are meant to be played, not collected.
So... my #1 choice for classic p&p RPGing would be Rolemaster and Call of Cthulhu and Paranoia for the more modern/futuristic approach. Specially Paranoia gave us many a good laugh, being a clueless clone can be mad fun.