I've played every game in the series.

That and non laggy controls is what makes me believe Brawl is the strongest in the series. Unpopular opinion? Yeah pretty much.

Brawl was revolutionary with Final Smashes (which were mostly more clever than the current ones), a huge campaign, and characters with special mechanics (Pokemon Trainer, ZSS, Lucario, etc.), so that seems reasonable.

I do like the new ones however in that they don't detract from the action. 5 seconds and they're done, in stead of having to run away from one guy for 30 seconds or longer.