I ran my own little horror movie review site for a good 4-5 years and got a decent amount of traffic (nothing major). I noticed that my initial reviews, when I would re-read them, would seem really bad in comparison to the more recent ones. I'm by no means a naturally gifted writer, and it was hard, after 100 reviews or so to keep the reviews interesting TO ME, as the writer. a few thoughts:
Over time, you'll develop a voice. I tended to try to be "funny" and I also did a lot of side research on actors or technical crew who went on to better things. I also read the book (if there was one) that the movie was based on and did a page-to-screen comparison and on some of the more obscure stuff I got decent feedback. You haven't lived until you've reviewed THE PACK _and_ read the book it was based on. My point - hit it from a fresh angle.
The other part is just practice and letting people critique. My sister was an english major and was invaluable in helping me sound smart. I Also revised, A LOT. I wasn't afraid to reconsider something or add to it.