1998 hasn't been topped.

That had Half-Life, Starcraft, Fallout 2, Thief, Grim Fandango, Zelda: Ocarina of Time, Metal Gear Solid, Banjo-Kazooie, Baldurs Gate, Resident Evil 2, Star Wars: Rogue Squadron, Xenogears, Turok 2, and much more...all released in the same year.

Many of those are foundational games in their respective genres, and are still considered among the best games of all time. 2015, in comparison, has a lot of really good sequels.