Origin on the House

Credit: EA
To be fair, this isn’t exactly a game. It might be better, though. Origin on the House is a free service that lets you download an old EA game or expansion pack for free every month or so. There’s no catch, either- just download the game and it’s yours forever.
The Elder Scrolls II: Daggerfall

Imagine Skyrim, just with very VERY old graphics. This second installation in the Elder Scrolls series of open world RPG’s set the precedent for the games in the series that would follow, like Oblivion and Skyrim.
As you would expect, the game has a huge amount of freedom – there are tons of items and equipment to pick from and the questing structure is similar to Skyrim’s (as you would expect). Basically, the game is Skyrim, just made a long time ago and with a different setting/story.
Everquest

The OG MMORPG Everquest is free to play. The predecessor to World of Warcraft is still a blast to play even though the graphics are subpar by today’s standards. The game still has a strong, devoted, and welcoming playerbase that makes the game very accessible to new players.
Even though the game came out almost 20 years ago, Daybreak is still releasing updates and expansions to keep its loyal playerbase happy.
Continued