I can see that ToME is by far the most popular (seen many lists like that).
But does that make it the best one?
I imagine it happens the same as with World of Warcraft a few years ago. 13+ million people playing, but not the favourite. Just had a very addictive gameplay for casuals, but no deep systems of anything. People loved Guild Wars or EverQuest (1&2).
SO ToME is the most played because it's the most accessible (great tutorial, popup system, unlocks), but ADOM is far deeper, altho it's extremely limited.
This is my impression, am I too far off?
Yes. I'd say pretty far off. Sorry. I wouldn't characterize it that way at all. None of these games are for casuals, though some are easier to pick up and play. ToME is not the easiest game to get into in the Roguelike genre. Probably Cardinal Quest, and the upcoming sequel, are WAY easier to get into. So is Brogue. None are mainstream type games and there's no real WoW. Besides WoW retains its market share in the face of better games because of the rpg aspect. People are invested in their characters, they have online relationships, etc...most other MMO's are just as approachable, or nearly so.
I play a lot of roguelikes and I very much dislike ToME4. Can't say why, it's just not my thing. I can recognize the high quality though. I also don't much get into Adom. I like the smaller, tighter, quicker games. I much prefer Brogue, maybe some DoomRL, Infra Arcana, that sort of thing. Or Slashies new game Rodney, which just today got a graphical tileset. It's still new and working out the kinks but it's a nice basic game. Crawl or even Nethack are more fun for me than ToME or Adom when it comes to the big games. Angband is also another huge game I haven't tackled.
So it just depends on who you are. Some are big and sprawling, some are tight and quick. Some focus more on graphics, etc...it's a very broad genre.