Seriously A lot of people do not seem to be giving it chance.

When I got it I managed up to about 800 too, and was finding it difficult to progress, so I left it, but after getting pro in all the other sports I went back to it and kept trying...
Eventually something clicked, I can't explain it but I understand how it works now, before I just flailed and got angry because some of my punches didn't even seem to count, but now I am a master.
In order of my preference;
Boxing>Tennis>Bowling>Golf>Baseball

Which is almost the order in which the complexity/depth of the motion sensing goes, because Boxing bowling and Tennis are in fact quite complex in what the Wii remote registers, everyone thinks tennis is just a timing thing to aim left and right, but it is much more. Golf is a little more simple, and baseball is very simple indeed.

My skill level in Boxing btw is now 2600+ It will take a while to get to 2700 though.

(Tennis I am about 2320, Golf about 1600, Bowling and baseball about 1200)

The only thing going against Boxing is the very thing that makes Wii Sports as a whole great, it's accessibility. Boxing is without doubt the most difficult game on Wii Sports but not because of technical hiccups or the game just being crap (which it blatantly isn't!), it's because it really does demand patience, practice and above all a level of skill and precision to pull it all off. It's very rewarding though, I think it might be the most satisfying game on the package! :)

Once you hit the Pro status it gets really intense, and yeah it'll definitely give you a hell of a work out too! Hit 1500 points and you face Matt the trainer, from then on it's stupidly hard (for me anyway, I've seen some people pull off insane combos!)

i love boxing, i play for 30 min. a time,

 The flailing will get you to about a 750 rating. Past that you'll need to learn how to dodge.

@TWRoO

I'm at 2100 right now. Are there any opponents who have rating much past 1600?

 @Vertigo-X

The makers of Fight Night have a game in the works called Facebreaker, IIRC. Visual style is reminiscent of Team Fortress 2. If they deliver good controls and a deeper game, then I'll be there. 

I actually really enjoy the boxing, didn't max it just went up to pro though

wow, 2100 is impressive. Yeah I managed to get to about 850, but I just never developed the skills to get any higher than that. Flailing doesn't work on tougher opponents.

Stof you are so lucky this boxing game is not online.... If not I could beat you...
I like the wiisport Box, but I really love the bowling

 No, the highest ones are around 1690 or so, but each time you play the same person they have a different level unlike tennis (although once you beat Sarah and Elisa you only ever play them in Tennis)

It's often I end up playing against opponents I am 1000 skill points or more above, They are always between 1500 and 1700... but I can't tell much differennce between a 1500 and a 1690, possibly because they all seem to have different tactics, so one might have really good defence, and is not great at hitting you, but when they do hit you they usually get a good succession in, and some are clever with their punches, so it doesn't matter where you dodge to, butit might be really easy to hit their head even when they have the gloves up.