I don't have any of the Elder Scrolls sagas.....do I need the previous sagas to follow the storyline on this $7 deal?
Which are the best (overall) gaming experiences in these Skyrim series?
Skyrim is just the most recent game in the Elder Scrolls games, and people have wildly different opinions over which ones they prefer. It depends on what you want out of the game.
If you've played Fallout 3, then that type of openworld, non-directional game is what you should expect with these.
Many people like Morrowind b/c the RPG elements are deeper there than in the other games--alchemy, enchanting, all of those things feel more essential, and unique. By the time of Skyrim, they are basically overpowered and without mods, difficulty disappears by about level 30 (roughly 15% into "the game"--depends on how you define it as main story arch or not).
Of course, you can avoid certain perk trees and make the game more difficult, but why should you? There are mods that address some of the balancing issues
Anyway, If you like Vikings and running around lopping off heads and killing dragons in an incredibly beautiful environment, then it's probably something you would like. The key with these is to come in without the completionist attitude (as I have)--with all of the quests and the size of the world, it is just too much for anyone.