A good form-fitting suit (along with the rest of the package: good shoes, belt, socks, etc) is like seeing a woman with a great tight dress on, hair/make-up done right, and is wearing heels OR a woman who dresses with some serious style from head to toe. Even if she is only a bit above average looks wise, your mind instantly correlates certain positive thoughts and expectations and you end up likely awarding her extra points; both in looks AND personality perception.
If you saw the same chick without make-up, in sweat pants, and wearing flip flops, that same chick would lose a few points on both fronts. This is all pretty obvious. The same generally applies in how women view men when it comes to clothing.
From my experience, only three things clothing-wise generate noticeable positive responses:
1) Dressing down in gym clothes and showing off figure.
2) Dressing up into full package custom suit or high-end GQ casual style.
(and to a less extent)
3) Wearing a t-shirt with something noteworthy on it (band, symbol, etc).
Anything outside of that and you just disappear into the sea with everybody else.
But bar none, the most noticeable clothing style that generates positive attention for me is a great suit. I gamed for so long WITHOUT a suit that once I finally started wearing one, it felt like I had cheat codes in a sense. The difference was that significant.
WAY WAY MORE: Hard eye contact, girls touching me, and compliments/openers by women.
SO many men in America can't dress for shit in general as it is. Many more that wear a suit look like shit. Pants too long/short, jackets too big/small, styles way out of date, square-tip shoes, super obvious cheap materials, grossly mis-matched colors/elements, too tacky, giant billowing shirts, etc. I'm not perfect but it only takes a little effort to cut above the vast majority of suit wearers in the US.
A man that has game, a decent body, and rocks a good custom suit can do A LOT of damage; especially in certain environments. No two ways about it.