I did say it's an action-RPG even 2 years ago, I have since changed my position to "there is no such thing as an action-RPG, that's an oxymoron". It's not "I know it when I see it", it's how you define genres as a whole, clumping together similar things and describing what makes them similar. Saying Fallout 1-2 and Gothic are "the same genre" is inane. Roqua is correct.
Other than their combat mechanics and camera angles, Gothic and Fallout have a tremendous amount in common, so I don't see what's inane about making them part of the same genre, especially if we acknowledge that they belong to different sub-genres. Saying Fallout is a turn-based RPG and Gothic is an action RPG actually does a very good job of communicating what makes them similar (all the role playing!) and what makes them different. Whereas saying Fallout is an RPG and Gothic is an action game obscures more than it illuminates. Since an action-RPG very obviously isn't going to have menu based combat, I don't see what could possibly be confusing or misleading about the term.
Saying Fallout and Gothic belong to different genres is like saying D&D and Spellbound Kingdoms don't belong to the same genre because they have very different combat systems. Spellbound Kingdoms places much more emphasis on immediately anticipating your opponent's next moves (it's a simultaneous turn-based system where your actions are limited by particular combat styles, as well as your last maneuver, so you can't go from lunging one turn to doing a backflip the next). Mostly you get fights that are all about guessing what your enemies and allies are going to pull at the same time, much as you need to anticipate your enemies and properly time your moves in an ARPG.
Here is the combat primer:
http://www.spellboundkingdoms.com/SKCombatPrimer.pdf
Hell, call it the difference between LARPing and tabletop if you want. IRL LARPers are still role playing.
While I understand your desire for a clear, simple definition, I think we could stand to learn from H.L. Mencken here: "for every complex problem there is an answer that is clear, simple, and wrong."