Sometimes when we mess around on the soccer field, somebody will dribble by the entire defense, stop the ball in front of the goal, then drop to the ground to head the ball into the goal.  Wow, a diving header!  Who cares.  Likewise, suppose that I get a king plus two pawns against a king, promote my two pawns to queens, sacrifice one of them, and still win the game.  Would this entitle me to claim a brilliant queen sacrifice that resulted in a won game?  Rhetorical question (I am not looking for an answer), but I do wonder if any body has ever tracked the frequency with which queen sacrifices are unnecessary.  That is, the game was won even without it.  In theoretical circles, it is often hard to define causality, but it would seem that we can all agree on a working definition of when the queen sacrifice caused the win, and when it was ostentatious.

Interesting topic.  While reading your post I was reminded of something that Znosko-Borovsky once wrote, "One must resist the temptation to be brilliant beyond reason".  I may be paraphrasing a bit but that was the gist of it.  Sort of an Occam's Razor for chess i.e. if there are multiple ways to achieve a goal, the simplest approach is usually the correct approach. 

With that in mind, I think we would have to label any Queen sacrifice ostentatious if there was a simpler, more direct and plainly visible option available that accomplishes the same goal.

Thank you -- brilliant mind's think alike!  And I like that reference to Occam's razor too!

How many true queen sacrifices have you seen in the modern era, say 1970s and after that weren't part of a forced mate which would be recognized as a moderately difficult tactic as opposed to an actual brilliance involving the foresight of an early queen sacrifice?

The first game that came to mind was Tal - Hjartarson, 1987.

The possible queen sac is at the end of the game.

I can't think of any.  But how many Queen sacs can you think of outside the modern era that aren't part of a forced mate?  Do you have to go back to the Romantic era to find any?  Even then, it seems like most Queen sacs are part of a mating combination.

the above post #5 ... is one of the games of the possibility of a queen sacrifice ... but, the sacrifice was not needed to win the game.

If I understand your question correctly, there was a sacrifice of this sort in a fairly recent game (within the last 2 years, I believe).  I don't recall the players or the event involved, unfortunately.  One player sacrificed a queen unusually early, for a positional advantage, rather than a forcing combination.

Anyway, until I remember that game, there's a non-forcing queen sacrifice by Nezhmetdinov:

Yes, interesting topic to bring up and Gonnosuke's invocation of Occam's Razor makes it all the more interesting. But, there are more things to chess (and life) than simplicity. I'd say we should also consider the symmetry of the game and, even, beauty. Einstein said one should make things as simple as possible, but not simpler than that. And that is open to subjective interpretation, maybe? Especially if one desires a beautiful game. 

Hmm...

There's a lot of psychology involved in such kind of play.  In the long run, the player will learn to love to do it simpler and show it in more efficient and beautiful manner.

 THIS IS AMAZING!

But are you really watching all the games? There are thousands of games played every year. Here is Inarkiev (2674) vs. Aronian (2741) from 2007

Here's Alexie Shirov vs. Nigel Short in 1999:

I blame the infernal "centipawn" for the dearth of Romantic chess in the modern era. 

The advent of computer analysis has changed our perception of The Sacrifice in subtle, but important ways.  Instead of focusing on the effectiveness or even the beauty of a sacrifice, we instead check to see if it was "sound".  To put it another way, we turn to the computer to find out how many different ways the sacrifice could have been refuted "with perfect play" despite the fact that such play is virtually impossible in practical terms.  The ease and accessibility of computer analysis serves to re-enforce the notion that speculative chess is not serious chess.

http://www.chess.com/article/view/spectacular-queen-sacrifice

This game comes to mind.

http://www.chessgames.com/perl/chessgame?gid=1008361

I'm surprised it wasn't brought up already