Time to give my two pence.
The aesthetics are rather plain -- you submitted this in 2008, but the graphics look like a 2000 novelty. Back in 2008 they had streamlined, better-looking skins than this! While I know you had a yellow-and-white BG on the back for Newgrounds colours, perhaps tone it down a little bit? With all the pictures on the Tetris blocks AND the background, it's kinda hard on the eyes.
In fact, I might as well be bold enough to say that the entire layout of the game looks like a website from between 1998 and 2000, when everything was running on HTML1. That kind of design normally warrants games no more than 2 stars.
This is where I gash the most points, unfortunately. HOW MANY VERSIONS OF KOROBEINIKI DO YOU WANT IN THIS DARN THING?!
Korobeiniki was the default theme and evoked a lot of nostalgia, sure, but there were *other* themes that invoked nostalgia, you know. Comparing the Nintendo and Tengen versions (for NES), we had Korobeiniki, Technotris, Bradinsky (which would've been nice!), Karinka, Troika... and the list goes on. The only other theme I ever saw was Technotris, which was great to hear, but other than that... the music selection has been left completely wanting.
Now granted, I know StencylWorks didn't exist back in the day. If you had Stencyl, you'd have been able to insert more MP3s rather than bulk the game up with WAV files. But taking into account the limitations you had then, surely you'd have just capped it at *two* Korobeinikis, and look for other classic Tetris themes?
Also, no sound effects when the lines are cleared? No drop sound effects at all? No fun. It's even less fun when the music has to be turned off just because of these versions of Korobeiniki that I'm hearing to no end, it makes any gamer fed up.
It played like a normal Tetris game..... except.... far laggier and far less exciting. I've noticed that hitting the Down key makes a hard drop, but here's the problem: *THE HARD DROP DOES NOT PLAY LIKE A HARD DROP.* It's just a slightly sped up version of the soft drop. If someone were to speed-play his way through a Tetris game because it calms him down, or because it makes the game more exciting.... well, this game fails on both counts.
And in addition to that, the lines clear very, very slowly -- and WHY THE BLAZES are they clearing one after the other? Is there no script to clear all lines at once?!
I have to gash even more points because, from what I read in a response you posted, you simply reskinned Gauss' Tetris game. You did nothing to make it better. And that's why a lot of Tetris games (with the exception of Mario Tetris and Fliptris) are simply not memorable. Now don't give me the old chestnut about 99% of Tetris games being slow and sucky, and that you decided to follow suit -- it doesn't make your programming or your skinning stand out, it only puts you in the light of a bad coder.
And on an equally serious note, the loading for this game was terribly long and drawn-out. What on earth is the file size of this thing?!
Long, drawn out, laggy, unexciting, uninspired design, too many uses of Korobeiniki. Overall, it's quite a chore to play this game.
Tackle all these issues, STARTING FROM THE DESIGN (since you skinned it!) and perhaps I could consider adding a few more points.