For me it's Diablo II. Granted I've played my fair share of D2 since launch, and also recently on a private server with a comrade from hexbear, but I still feel like years later the game didn't grab me as much as D1 did.
Granted I don't hate D2, but for a game that I keep coming back to, D1 takes the prize.
I never played the warhammer fantasy tabletop (I did play 40k, though it's been a long time since that and all the actual games were online through vassal), but I did read the rules and army books back in whatever edition was contemporaneous to 40k's 5th edition, as well spend a bit of time reading forum threads talking about the meta.
And that's about what I remember about Cold Ones: they're a really cool concept and design that just gets overcosted and has too many drawbacks.
In TW:WH2 they've got the same issues: too expensive, too slow, too many drawbacks, in a meta that heavily leaned into ranged spam, especially for Dark Elves who had one of the best and most spammable ranged infantry units in the game. Some armies relied on pitting enemies with chaff to slam with a hammer or rain tons of fire down on them, and for a few the chaff they pinned enemies with was also going to grind them down on its own, but others were just "kite and rain fire down on enemies, avoiding getting pitted" and Dark Elves were one of those.