There's no right answer, but it's fun to talk about when I can't get out.
For me the three "food groups" are safety, repair, and recovery - in that order. So always bring - Safety - (water, first aid kit, etc..), Repair (basic tools, tire stuff, etc . . .), and recovery (shovel, snatch strap, shackles, etc . . .) But how much beyond the basics you go in each area depends . . .
It depends on where you're gonna go, what you're gonna do, and who you're gonna do it with. You need different things in the dunes than you do in the forest, and even in the forest, you need different things for rock crawling than you do for leaf looking. Its all about risk, and what level you are willing to accept. You need more stuff if its hard to get outside help, and you need a lot more stuff travelling solo than you do in groups.
Then there is a kit that evolves with your experience of what you have needed doing similar stuff in the past. Everyone is going to end up somewhere different based on how they use the vehicle. Brent mentions above that he has only needed his winch once in 10 years. I've used mine quite a bit, and I get itchy if I leave the driveway without one. But I never carry maxtrax or a high lift jack. Not that they aren't good gear, but I always had another way more suited to my situation. If I am going to do something really hardcore, I'm more likely to pack a pull-pal or a chainsaw.
Maxtrax are a good example. I used to do a lot of desert (dune) driving, but 95% of the time we had at least three cars. That was almost a rule. The primary recovery method was snatch straps or winches. Which was always easy because there was always another car. We drove with people who had Maxtrax, but in a few hundred trips, they never came off the roof rack. For solo travel, max trax look like they would have been a game changer. But we did that so rarely that we never bothered to get a set. For what we were doing, max trax were just additional weight. For a solo traveler in the same area, they would have been a smart move.
Likewise in that same area, our needs changed depending on what we were doing. On a club run, we would always have recoveries because we were out there to do challenging things. But on camping trips, we would drive the same areas and never get stuck. On those trips, we were probably overkill on recovery gear.
Unless you are trying to challenge yourself and get stuck, I think the ability to do repairs in the field is probably more important than a large stockpile of recovery gear. Basic tools, spares, fluids, compressor, tire repair kit, etc... This again will be different based on what you are doing. I used to rock crawl with a complete set of spare axle shafts, u-joints, hoses, belts, hubs, lots of fluids, etc... I probably carried so much weight in spares and tools that it caused the breakage that I was fixing. But we always drove our junk off the trail. These days I don't rock crawl, and I'm not going to car camp with a footlocker full of axle shafts and half of NAPA. Now its a thoughtfully filled tool roll, some fluids, belts and a u-joint or two. I use the weight savings for beer and Overlandy stuff made of titanium and bamboo.
I'm struggling right now with a rear tire carrier. It's a great, high quality piece of gear, it frees up space inside, and I can carry more stuff, but its a real pain at the grocery store, and its overkill for the way I use the truck. I find myself with cargo riding around in the front seat because its such a pain to swing open the tire carrier. I think I'm gonna rebuild my drawers so the spare will fit inside, and the tailgate becomes convenient again.