Skully: I'll let you know when I get good.
edit:
More serious answer.
I'd say that me and Imadh got good in about 2 years. We played a lot in our various communities and had several training partners and rivals at the time (Mike, coolhat, Daniel, Nate, Jake, James, etc). This was also around 2007, which was what I affectionately refer to as "The Technical Revolution", when a lot of the commonplace tactics we see today (actual pillars, Peach's fast pressure, low pressure, etc.) were born. So there was a massive information dump in that year (M2K being the best helped because it became kind of cool to know stuff) so a lot of learning was going on at a level that was a bit higher than practicing your basic tech skills. Gayness was becoming widespread, and gayer strategies were becoming the norm.
During that time, we had my biweeklies to go to, semi-frequent tournaments (and a few big tournament series run by good TOs at nice venues) and a lot more general interest in the game. This, plus the power ranking, generated a lot of drive to make people want to improve. We were also younger and a bit more absorbed in our egos; people got really salty about losing stuff. I also tend to think the skill gap was less daunting to the up & comers; nowadays it's a nightmare (not to toot my own horn or anything).
We also had top level competition that was a step above us to beat us up and remind us that we weren't that good, no matter how good we got. Quebec. And later the states. So there was never satisfaction even if one reached the top spot on our local PR because Quebec would still come to town and take our money.
So in these very good, near-ideal conditions that promoted drive and growth, with consistent practice, constant tournament attendance (some slips but relative consistency; certainly better than now), and some decent talent towards the game (I think Imadh and myself have some talent) it took us 2 years to get good. And then another to get good at being good.
In short... this game is stupidly hard to learn. I think there's like a handful of people in this community who are skilled and the rest of you are still... facing some serious gameplay problems right now.