What's niche? You mean niche by design regardless of sales (you could put some pretty high selling games in the "niche" genre) or just niche by sales (because there are games that should sell well but may not have)?
Xenoblade Chronicles X is, by design, fairly mainstream. It's a science fiction open world RPG, which are literally three pretty main stream terms. But the last Xenoblade was sub-1mil (mainly due to supply constraints, zero marketing or fanfare, and looooooong delayed and low budget localization).







