Basically, each game (bringing it back to the original) can only target those users who like that particular type of game. Whether it means they have good story lines, or a good game play, or a particular style of gameplay, or whatever. The 'forumula of success' is actually 'know what your buyers want'. Anything more specific can really only pertain to individual games.
This is a very good point, and a very good way to summarize what I was trying to say.
The "formula of success" could also be "do what you want, you will always find an audience", but unfortunately, this audience will not necessarily mean success, as seen with works of art that attract very small audiences, or any type of work that failed in its time, and was rediscovered long after it could do any good to its original creator, for example.
I agree with your idea of an "overlap" of tastes. I would say that there is not the slightest form of reason in what governs the tastes of an individual myself, but I understand what you mean.
Also I find it pretty interesting that I do not feel the same way about the Deus Ex series, what interests me with your first example is how two different people can have two different views about the exact same thing. I loved Deus Ex too, but the context is different for me. I discovered the game long after it was released, and bought it here, alongside its sequel, which I knew was not as appreciated as was the original. When I first played Invisible War, I expected a game so horrible that I liked it, not seeing its flaws as being as unforgivable as I had been led to believe they were. To me, it was not a perfect game in the slightest, but I appreciated it anyway.
However, I do not like the ones that came after. In my opinion, they feel and look so different than the two developed by Ion Storm, that I cannot even connect them to the title "Deus Ex". To me, it is like if they happened to have a similar title, but were unrelated to that series. Even taken as independent games, I do not like them. I find them too easy and predictable, even on the highest difficulty.
About your second example, I obviously cannot relate. I am a man, so I do not ride horses, I eat them. Furthermore, I need women to be at least busty and mostly naked to be able to appreciate a game. As for men, it is common knowledge that they have to look like walking fridges with beards to be respectable.
Sorry for all of this. That is what I call "humor", and the sad part is that I find myself funny. Just know I was not serious.
The thing is, I agree with you on this matter, though. Not the horseback riding part, although I do like horses, but about the mostly naked women and the solid-block-of-ore-like men. With the exception of humorous games, I need at least a slight degree of realism to be able to immerse myself in a story. If I'm facing something in a game that makes me stop believing in the overall consistency of the world it is set in, I find it hard to play it to the end.
I think I have nothing more to add to this topic now, not without derailing too much anyway. Furthermore, it would be a shame, as your conclusion, which I highlighted above, was really good.