Two come to mind.
Eternal Darkness, probably invested 100+ hours into that. I adored everything about that game. Each playthrough after the first was 100% without exception. Even the chapters I didn't like I soon warmed to.
The Binding of Isaac. Considering this was a game I played daily for 5-6 years, I'd say throughout its various iterations, game time probably would check in around several hundred to thousand hours. Especially, as there was a patch of a year or two wherein it was my only game. My gaming obsession. I discovered it at the right place, at the right time, and it got me through some rough years.