Bethesda makes an appearance more than once on the list due to their ability to take somewhat niche franchises and turn them into some of the most anticipated releases in gaming culture.
One of these franchises, of course, is the Elder Scrolls series. Now, unless you're a hardcore Elder Scrolls fanatic, you'd be hard pressed to name the subtitle to the second game in the series or if there even was a second game in the series. Everybody has heard of Morrowind, Oblivion, and Skyrim, but what about Daggerfall? No? Well neither had I - I had to look it up for this list.
But then came Morrowind with its sprawling open world that was unlike anything before it, and from that point forward, Elder Scrolls has been one of the most popular RPG series out there.