Having played a Mahariel during my first playthrough of DA:O (she is my canon Warden and remained together with Alistair as Wardens), the Dalish have always held a special place in my heart.
Also, FYI I don't play humans in games where you could choose your race because I find them boooooring af since I'm already human and most video games have you play as a human anyway. Elves for life!
(I still give a huge middle finger to DA2 for making me get stuck playing as a human.
)
I've always thought that Tabris was more popular than Mahariel due to the number of people I've heard back in the day complaining that the Dalish origin was "boring". But I wouldn't say Mahariel was unpopular. Like, seriously, the Dalish origin is NOT the least popular origin in DA:O. I've seen a good number of fanarts and fanfiction of the Dalish origin. Mage origins, as mentioned by someone earlier, was pretty popular too. Of course the Queen Cousland fics and fanart far exceeds the number of those created for Tabris, Mahariel, Surana, and Amell. (For obvious reasons.) At least during the time of DA:O's popularity.
Then there's the dwarven origins. I think Casteless Dwarf origin might be the least popular, from what I've seen. 