Let's not pretend that Thanos is completely immune from being a jobber himself:
Yeah, yeah, animated Darkseid (voiced by Weird Al Yankovic) got "killed" by Cyborg in the goofy Teen Titans Go! cartoon (which has next to zero continuity that sticks), but Thanos' defeat to SG is 616-Marvel comic book canon.
Let's break it down some more:
1970-1989: Darkseid, by a huge margin, across comics and animation (DC SUPER POWERS show)
1990-2009: Roughly tied: Thanos in comics and video games (Capcom's MARVEL SUPER HEROES), Darkseid in animation (S:TAS, JLU, etc) and live-action (SMALLVILLE season 10)
2010 - present: Thanos, by a huge margin, across comics and live-action (MCU cameos in AVENGERS, GOTG, etc)
I feel that Darkseid v Thanos is a more cosmic villain version of the older Sub-Mariner v Aquaman dilemma, where the original (Namor) is eventually surpassed by the copycat (Arthur) on every level that matters: mostly popularity IRL, media exposure, and better writing in the comics.
Also, Thanos definitely nails the "Me Vs Everybody" aspect far, far better than Darkseid does, as Uxas always brings his inner circle and parademons, which really seem to weigh him down more than help him for some reason. Thanos is just him and Death.