Fallout New Vegas director Josh Sawyer has suggested that Diablo 2 actually helped drive sales for his first D&D RPG, Icewind Dale, by launching on the same day.
According to Wikipedia, Diablo 2 launched on June 28 while Icewind Dale launched a day later on June 29, but the sentiment still stands that the two games launched very, very closely to one another. And in an interview with Edge Magazine, Sawyer acknowledged the perception that an RPG like Icewind Dale from a relatively small studio (at the time) launching at the same time as a juggernaut sequel like Diablo 2 would not be good for the former's sales.
"Icewind Dale launched on the same day as Diablo 2, which sounds like it would be catastrophically bad, but it actually did pretty well," Sawyer said, suggesting quite the opposite: that the timing actually benefitted Icewind Dale. "There were lines and lines of people to get Diablo 2, but a lot of them were into fantasy and isometric games, so they were like, 'Icewind Dale - what's this? Yeah, we'll pick that up too."
These days, video game release dates are shuffled around frequently to avoid clashing with other launches. Probably the most high-profile example I can think of in recent memory is Larian moving around Baldur's Gate 3's release plans to avoid clashing with Starfield. Last year, THQ Nordic delayed survival horror game Alone in the Dark out of 2023 entirely because there were "too many amazing games" launching that year, and boy, ain't that the truth.
Now get our of your own way and go play the best RPGs out there.