I learned ATC with Flight Unlimted II and procedures with Fly! which had very realistic systems and panels.
Lol that was the first sim I really got into also. it was a lot of fun and set the bar pretty high because very few sims since have had such natural sounding ATC, complex/evolving/realistic AI traffic, and such realistic flight model damage with stressing the planes ripping the wings off, control surfaces off, bending the prop, ect. I liked it much more than Flight Simulator 98 back then as a tot.
Now as a grown ass(you can totally say ass on here) man, I love P3Dv4. X-plane 11 looks nice and all and it is a lot of fun, however while I do prefer X-Plane 111 for just hand flying airplanes around the pattern and stuff due to the flight dynamics and for practicing emergencies as well, but I don't think the immersion with X-plane is nearly as realistic as P3D, especially with what all the add-on stuff brings to the table. P3D out of the box is another world from what it can become if you know what to add to it, even the default airports look amazing with stuff like "REX Direct Textures" and stuff.
There are some really neat planes out there,
Captain Sim also makes some great stuff with all the systems working and the aircraft handling very realistically. A lot of old stuff like the L-1011, 727/732, 707, ect. I use the 732 all the time in the virtual cockpit view to look at the six-pack and handfly IFR flights/approaches. Definitely a great training tool for IFR flying, especially flying online with VATSIM where you actually have to file flightplans, get your route clearance, and let ATC run the show with varying levels of English and experience, just like real life.
Lol the new sim is a lot cooler, I want to make more videos but I have no idea where my headphones with the mic are...