I got MW1 this christmas and I honestly love the game (if only I had faster internet connection, I could play for hours and not get frustrated at it, lol). I can really see why it usually gets more love than the newer CODs, basically because it made the series in what it is today with actually innovating a lot, but there are also less annoying kill streaks, campers and quickscopers (even though they are still there) and the guns to me feel better, like I can actually hit something even with extremely high ping. Not to say it's perfect, but damn I really enjoy it. MW2 is my personal favourite, but this game is pretty legendary. I play on Xbox 360. The game is pretty 'old', so are any of you guys still playing?
Currently I'm trying to get a hang of sniping. I think the M4 and R700 are the best snipers because they have a one-hit kill with stopping power (not always though, but this must be my internet connection). When not sniping I use the AK47 (surprising huh?), the MP5 (for short range/rushing only) or the SMAW, which is a beast if you're going on a killing spree.
The best thing with this game is playing online with friends, so you can do super awesome tactical stuff. And it's always good for a laugh, or just to share frustrations with.