I used to love GURPS. Then I grew over it, decided it was too heavy for my taste, and it's often better to tailor a system to a specific setting or play style.

Though maybe I should give Dungeon Fantasy a try.

@Craig Maloney - I had a similar experience with Gumshoe. Now it rivals Fate and PbtA as my favorite system.

@Craig Maloney - I don't know if you've seen the playtest for Swords of the Serpentine, but that one is great. They asked me to hold off on posting my blog publicly until it's out at the end of the month, but those are some of the most evocative rules I think I've ever seen.

GURPS fills several feet of my bookshelves, because the source books (especially for different time periods and cultures) are terribly useful for reference in play. The mechanics of the system suffer from two things I have real problems with, too few attributes that are the basis for skills (everything is either INT or DEX).and that as a GM you have to go thru ALL the character data and make a list of what is or is not allowed in a setting at start. Giving folks a 5 page setting handout of "Can't Have This' can be very annoying to players.

As a Player I found my favorite characters were ones where I simply made all the base stats a 12 at start (so the calculations would not change and I had a good 75% chance of success in most things unless I put extra points into the specific skill). I found most GMs avoided the nightmare of task penalties and bonuses, since that made the probability math more complex than they wanted to deal with (as a -1 or +1 was not a straight percentage value of change).

The last time I played GURPS was about 3 years after the 4th Edition came out.

I've started roleplaying with AD&D2 but then played especially 3rd edition, like A LOT. Then I grew tired of the unneccessarily complicated mechanics and lots of subsystems, and now I play much lighter, narrrative-focussed games.

As for boardgames, I think 7Wonders is the one that falls into this cathegory for me: i played it at a convention and immediately bought it. But then I played it more times, and I don't really...understand it? I feel you can't really make a long-term strategy, you just have to optimize each hand. It seemed a lot more varied and profound to me than it actually is.

Muchkin is another game i had a lot of fun playing for the first 3-4 times, then got really bored: each game is basically someone getting to level 9, everyone else using everything in their hand to prevent them from leveling and then the next level 9 player winning the game.
I think Munchkin is funny to read, not enough fun to play though

@Craig Maloney - It's supposed to drop on the 31st!

I used to really like the World of Darkness games. Really really like them. Spent hundreds of dollars on them. This is the late nineties, when they were still the New Hotness. I can barely look at them these days. They're ... not great. Setting has some cool ideas, but the system ... ugh.

On the flip side, I bought Ron Edwards' Sorcerer when I was young, and wasn't impressed. These days, though, the more I read, the more I see. It's not perfect, and, in many ways, it's showing a bit of its age. But I can definitely see how this inspired the Indie movement.

Talisman is the game the exemplifies a game I used to love that I won't even play now. I still have my copy of hte 2nd edition with all my painted metal miniatures but that's just due to fond memories. Every 10 years or so I break it out, I have a great time for an hour or two and then consider quitting as the game just keeps going on and on.

As for one I didn't like but then came around to: Cry Havok. I bought a copy online and for whatever reason the shipment got delayed. In the meantime I played a friends copy and had a horrible time. The factions were so asymmetric that I couldn't figure out what was going on, fighting seemed neat but unfathomable, and card combos I thought would work failed time and time again. Then my copy showed up. I almost sold it still in shrink based on that first experience but found no takers at full price. Not able to get my money back I figured I would play it. This second time it was with a totally different group, plus I had read the rules myself instead of being taught and everything just clicked. Things I found were a problem were actually features of the game and not flaws.

That just goes to show how important the teaching is of a game and how games can play very differently with different groups.

Pathfinder. For a long time 3.x was my preferred D&D because it was easy to design for. Pathfinder came along and buffed it up (and I admit, I was somewhat cheesed with how WotC botched 4e -- 3e marketing was great, 4e marketing was underpants gnomes all the way down and they lost me).

Then it went to 11 and got crunchier and crunchier with more exceptions to remember. It became something I no longer wanted to play because of the expertise required. I went back to old school games.

That said, I do still mine Pathfinder for other game projects. Just because it's more fiddly than I want to play doesn't mean it's not a good place to get ideas for other systems.

GURPS. When they announced D&D 4 was coming down the pipeline, we jumped ship and bought into GURPS. But, because we didn't game very often, we never really figured out how to do GURPS the right way. This meant we spent WAY TOO MUCH TIME flailing around in the rules book vs. time playing fluidly. That's more on us than the rules, but there are LOTS of rules. We finally realized that if we stuck to the basic stuff, we didn't have nearly as many issues with it. But it took a while to figure that out. Plus, it just has a different feel than other engines we knew at the time.

I bought the core books for D&D 4 years later, but I have never played it. My read of the rules made it seem like they drifted too far into video game territory. D&D 5 seems to have corrected most of what I disliked there, but not 100% (mostly around things that reset immediately at the end of a combat sequence).

D&D 3.x had too much reliance on miniatures. I enjoy miniatures -- to a point. But you basically couldn't do combat in D&D 3x without them, due to how many things relied on knowing exactly where things were. Feats, primarily. Oh and gods there were too many feats and prestige classes!