While I was faced with some difficulty early on, I soon came to the conclusion that it
HAS to be Fallout. Just think about it!
Most of the 'franchises' here decline in quality, some more than others, but going from playing Fallout 1, 2 or Tactics to the atrocity that is Fallout 3 is... something all right.
Also, I'd rate
Jagged Alliance as a fairly close contender, but at the same time, I'm not too sure about my stance here, as I haven't played the first.
Some additional thoughts below. Please note that none of these has such a massive drop in quality as Fallout, so they aren't elegible:
Elder Scrolls: I liked Morrowind for its original setting, and because of that I actually bought the collector's edition of Oblivion, which, as we all know, was a generic, level-scaled disappointment. I actually think that Skyrim was an improvement, but its ending was outright bad. I'd say that as hiking simulators, these games are good. As rpg's... not especially.
Baldur's Gate: Number one is good, the second one isn't bad, the beamdog 'enhancements' should translate into a one-way ticket to a labour camp if there was any justice in this world.
Dragon Age: It was bad from the start.
Diablo: Number one and two are good. I remember playing D3 on hardcore from beginning to end, and the only monsters that were a threat were the 'special' champions. Yawn. The new art direction and overall lack of grimness buried the rest.
Mass Effect: A steady decline in quality until the plunge at the end. At least the deranged
fans Talimancers brought some amusement to us in the Best Thread Ever with their sick creations. It should be noted that the last game was so appalingly bad that it couldn't even inspire the perverts, maybe because being such a vile creature is now the new 'normal', or at least not far from it. Where I live it is even sanctioned by state, and the filth even appears in kid shows on TV.
Heroes of Might and Magic: Some like II best, but number III is where it's at for me. To be fair, VII is a lot like III, so this 'franchise' gets a pass from me, even with the bad games in between.
Sonic the Hedgehog: I recall it from the Sega Megadrive days of yore, but I haven't played it since. Thanks to the efforts of
sgc_meltdown and other connoisseurs, I'm aware of the bizarre following it has. Most raped? Maybe literally...
Doom: I hear that the new games are good, but to me they are too far from the originals to be of any interest. They've taken away the horror elements but kept the action, so I wouldn't compare that with, say, FO1 - FO3, where everything good was removed and nothing was kept, except at a shallow, retarded level.
Warhammer: (If it means 40.000) Everything that comes after the 2nd edition is shit in some way or the other.
Civilization: Haven't played the first, the second is really good, number III was all right, and IV with all expansions is a favourite. V and onwards is dumbed down shit.