As someone who's owned a YJ, a TJ, and a JK, plus worked at a stand alone Jeep dealership from 1998 to 2002, here's my thoughts:
YJ: 1990 Wrangler Sahara, 4.2 258, 5 speed. Highly modified suspension and drivetrain. Tons of fun!
Stock form:
Modified:
TJ: 2000 Jeep Wrangler Sport, 4.0 5 speed, also highly modified suspension and drivetrain. More fun and more capable than the YJ.
JK: 2012 Jeep Wrangler Unlimited Rubicon 3.6 Pentastar, 6 speed standard, completely stock. MUCH more comfortable than the YJ or TJ, not as capable off road with stock suspension. With a small lift and larger tires, would have been MUCH more capable than either previous Jeep.
My vote, try to find a standard transmission TJ six cylinder, plan to do some frame repair, and build a fun vehicle dependent on your needs. If summertime cruising with fire roads being your toughest offroading, you don't need lockers and all that jazz.
Of course, if you want to be truly badass, build a one ton drivetrain, sprung over, 4BT, Scrambler. Stick a Blue Heeler in the back that will eat the face off anyone who comes near it, and roll coal on all the Priuses and Teslas. YOLO. Your choice.
If you've got any questions, PM me. I'm pretty well schooled on 1987 to present day Jeeps, and there is a lot of wrong information in this thread.