There have been 27 instances of MCU & DCEU titles in the Top 10 at the same time since Man of Steel, the first DCEU film, was released on 06/13/13 (of course, Marvel beat them to the punch by more than 5 years with Iron Man on 04/30/08). There have been 8 opportunities for this to occur out of 15 possible head-to-heads (only 15 DCEU movies were released, with the last being Aquaman and the Lost Kingdom during the Christmas 2023 period). For the intents of this analysis, all Sony and Fox releases (Spider-Man, X-Men, etc.) have been ommitted from calculations.
It should be noted that the two universes never opened movies on the same weekend. The closest was a 2-week gap on one occassion: Justice League was released 2 weeks after Thor: Ragnarok. Of the 8 cases wherein the MCU & the DCEU occupied the Top 10 together, Marvel released their film first 6 times, though Shazam/Endgame is an outlier as Shazam dropped in Captain Marvel's 5th weekend (then dropped below Captain Marvel for a weekend when it surged back to #2 in conjunction with Endgame's release).
DCEU & MCU movies have spent a total of 15 weekends together in the Top 5, and only occupied the Top 2 twice. Only ONCE did one universe knock the other out of the top spot when Black Panther: Wakanda Forever pushed Black Adam to no. 2 in that movie's fourth weekend.
All this is to say that comparing the relative successes or failures of the MCU & the DCEU on a movie-against-movie basis is kinda apples & oranges. There are so many mitigating factors impacting profit & popularity: release dates, sequelitis, perceived quality pre-/post-release, good and bad press (I'm looking at you, Ezra Miller and the bro-trolls who hate Brie Larsen/all women).
Perhaps some better metrics would be average domestic/worldwide box office (MCU: $365,352,497/$884,429,364 over 36 movies, DCEU: $185,766,5/6/$480,310,217 over 15 movies) and highest earners (DC has a single billion dollar movie worldwide [Aquaman at $1,148,861,807, while Marvel has eleven with all but Captain Marvel [$1,129,576,094] having a higher take). I'm a DC guy from way back, but ti's hard to argue with those numbers. Marvel wins.
MCU vs DCU is starting out with a bang but, with the release schedule as it stands, there is no instance scheduled so far of a head-to-head for the foreseeable future (Supergirl & Spider-Man: Brand New Day are 5 weeks apart next summer). Maybe, for the health of the genre, it might be best if they just... stay out of each other's way.
