Polo Rules

First, to me, a game who ended by a fast 5-0 is a boring, so why should we have to wait 5 more minute to continue to watch this game 5 more minutes to finish to a 10-0.

Because it will allow the game to reach it's natural end and will show more disparity (or not) between those teams (this is hugely important for tournaments that use Podium's GD as the tie break). It also ensures tournaments can be scheduled more predictably and all teams the same amount of minimum court time for their registration fee.

Many times I've heard around courts people complaining because a team looked pretentious because after 3-0 they were trying some spectacular plays.

This is not a problem inherent to unlimited goals. (Teams should be more professional/sportsmanlike regardless.)

We played london BFF with unlimited goals, we won the final with a big gap, something like +10 or even more. I remembered how Luis was pissed on the court and how bad I felt between, it's a final I need to play my best and what the point of killing them, everybody is looking at this game.

Your individual experience may have been negative, but that is not a reason to disregard the benefits of unlimited goals... it is highly unlikely for finals to be so uneven (with few exceptions). You should learn to enjoy winning and the other team should be less flustered when conceding goals (this is a problem for most teams in polo as Cosmic Matt pointed out earlier, teams that stay calm under pressure should be allowed the opportunity to close the gap on a team with a convincing lead).

I think the game will move to a most defensive game with this rule.

There is no evidence to support this claim, actually the opposite is true (as now a team have the opportunity to increase their GD more substantially in each game and defending teams will be punished accordingly).

My best polo memorie was final EURO 2010, between L'Equipe and Cosmic. 5-4 after a 40min game. We would have never seen that game with an unlimited goals game.

True enough, but that is not an accurate representation of the two team's ability to "win" the average polo game. I like a spectacle as much as anyone else, but there is very little reason to move the goalposts of a competitive event (during the later rounds) to appease the spectators of said event.

We have also had finals that were won in a couple minutes because one team had a shaky start and both teams are awesome on the attack (but not in defense), the ball's out approach of first to 5 has as many poor results as it does exciting/good results. I can remember many 30 minute games where the crowd started shouting "boring" (for example).

My preference is giving a team the ability to come from 5-0 down to win 6-5 (or whatever), that would truly be an exciting game, or a game where both teams constantly chase each other for the win (ending in double figures even).

Statistically/logically there is no reason to use first to 5. But emotionally I can see the argument (I think using unlimited goals for the Euros or the Worlds is a bad idea personally: it would irritate lots of people.)