1. The Elder Scrolls: Arena
The game that started it all!! The general blueprint of the Elder Scrolls was laid out here, and hasn't changed all that much over the years. Clearly it isn't as advanced as some of the newer games but it laid the foundation for future games.
2. The Elder Scrolls II: Daggerfall
While Daggerfall refined and improved a lot of what made Arena such a good game, the world it was set in was fairly bland, and often times felt quite repetitive. Most of the towns you visit feel exactly the same, and the dungeons get boring once you realize they all follow almost the same layout.
3. The Elder Scrolls IV: Oblivion
Now this... might annoy some of you. While I think this game is really good, and at certain points great, the combat system is what fails the game the most. Throughout the entire game every character levels with you, and the combat makes it feel like you are doing almost no damage while random villagers would be able to one-shot you. Oh also the main storyline kinda sucks.
2. The Elder Scrolls V: Skyrim
This is truly an amazing game. Despite slight narrative issues that make following the main storyline a little confusing, Skyrim is just a stunning open world to just exist in and interact with. Side quests are extremely detailed and almost never feel repetitive. Also dragons are pretty cool.
1. The Elder Scrolls III: Morrowind
This was a pretty obvious #1 for many. Sure there are plenty of little issues to pick at but Morrowind provides an experience so immersive and truly unlike any other entry in the Elder Scrolls Series, or any other RPG. It is more beautiful, interesting, complex and political than any other Elder Scrolls game, making it a pretty easy #1.