Well, in my case it is strictly matter of genre - I played lot of RTS games in those days, and Warcraft was, and still is, RTS game for me. I didn't care much for, then announced, Warcraft P&C Adventure (though that is one of my favourite genres) and I didn't care for WoW since I don't care for MMORPGs.

Lore was, honestly, completely irrelevant for me while playing Warcraft 1-3. And I like to dive into lore when I play RPGs, but I never cared for that in RTS games (well, except for AoE, with that nice excerpts from Earth's history).

Diablo, easily. It was always a go-to franchise for our LAN meets back in the day, and we spent countless hours playing both Diablo I and II. Since about 08 or 09, all my friends are scattered around too much, making LAN meets near impossible. Also, Diablo III released and was a shit-show (in my opinion), making me lose interest in it completely after only a few weeks. Both my friends and I started playing Titan Quest instead, and more or less stuck with that for many years. I've never played Overwatch, it's not my type of game, and I was never any good at RTS games, so Warcraft and Starcraft are out the window as well. I gave WoW a shot back when it released (during one of our LAN meets, actually), but grew very bored, very quickly, and never played again.

Luckily, Diablo IV has rekindled some of my love and interest for the Diablo franchise, I'm enjoying it more than I thought I would, it has really solid combat and is technically quite impressive. In addition, they've put actual efforts into characters and story for the first time, it's not going to win awards, but it's a real step forward in the genre as a whole. There are also some glaring issues, though, so we'll see how I feel in a few weeks time.

From my end, I really got into the lore within certain RTS games, primarily when it came to C&C, Warcraft and Starcraft, since those game universes had abundant amounts of lore for them (And Age of Empires for history buffs that want it). 

Don't get me wrong, I still love gameplay as much as anyone, but whenever I play a game that's trying to tell me a story, I'm most likely to try getting into it, rather than seeing it as window dressing and focussing purely on gameplay.

Diablo by a landslide.
The original game is still to this day on my all time top 10 games ever.
Diablo 2 was really great.
Diablo 3 even as not as good as the others still became one of the games I spent the most time on ever, probably nearly 1000 hours.
I'll be waiting for a good deal to get Diablo 4, but I really liked what I've played on the beta, 15 hours in 1 and a half day was by far the hardest I've sunk into a game in a while.

Starcraft has been the one that's pretty much been consistently awesome for me. These days I've played Overwatch a ton more, though that one is more of a love-hate relationship with me.. 

Warcraft 1 and 2. StarCraft and Brood War. Warcraft 2 was my first online gaming experience (I think via expansion) and pre-battle net. Although I played way more StarCraft online. I grew up with those games.

I also played Diablo, Warcraft 3, World of Warcraft, and StarCraft 2 but didn’t get into them.