I'd just like to interject for a moment. What you’re referring to as ESO, is in fact, The Elder Scrolls/ESO, or as I’ve recently taken to calling it, The Elder Scrolls plus ESO. ESO is not an Elder Scrolls game unto itself, but rather another shitty component of a fully functioning Elder Scrolls game made useful by the Elder Scrolls franchise, lore, and history components comprising a full Elder Scrolls game as defined by Bethesda.
Through a peculiar turn of events, ESO is now being referred to as an Elder Scrolls game, and many gamers are not aware that it is basically a cash grab developed by Zenimax. There really is an Elder Scrolls game, and people are playing it, but it is not part of ESO.
The Elder Scrolls is the franchise: the thing that ESO rides on. The franchise is an essential part of ESO, as without the franchise, no one would have played the game. ESO is normally used in combination with the the Elder Scrolls franchise: the game is basically the Elder Scrolls without the Elder Scrolls.