Bob I agree with you 100%.After playing 5 games my, every single one of my friends said they are bored of the game.
Main reason is because everything is the same. There are only 3 races and each are exactly the same...
I'm wondering whether I'm playing the same game as you.

The races are by no means the same at all. They all have different strengths and weaknesses in multiple areas, from their ship abilities to their economies to their technology. While many of these differences can be quite subtle, the interplay between them creates major variations in each race and how they play, and thus the strategies that are effective with each.
I agree that the differences may not jump off the screen at you, but the more you play and learn about the game, the more significant they become.
Also the battles are all exactly the same.
Again, I can't help wondering what game you're playing. Fleet size and composition make a significant difference to what tactics will be effective, and your decisions during a battle can greatly affect the outcome.
There is no such thing as strategy in this game, it's still who ever has the biggest zerg wins easily.
On the contrary, this is exactly the reason I've been getting more and more tired of the click-fest of 'standard' RTS games, and why Sins comes as a breath of fresh air. It's a real-time game with real strategic depth and variety.
The hardest AI is a joke!
This is the only thing I agree with, to some extent - I wouldn't go so far as to say it's a joke, but it's not as tough as I'd like it to be. However, the devs are aware of this and the next patch is planned to include the first of what I expect will be many improvements to the AI.
In fact I think getting a 90% is ludicrous from IGN. Clearly they played 1 game against each other and said wow this is fun. They never played a couple games, otherwise they would surely catch that it gets super tiring fast.
On the contrary, I suspect that the IGN reviewer played a lot more than five games, and it's you who haven't played enough to really appreciate the game. IGN is far from the only place to give it a good review - it's averaging 89% on Metacritic and 90% on GameRankings, and the lowest score I've seen it receive is 80%. Or do you think that every strategy game reviewer in the entire industry is incompetent?
That said, everyone's mileage varies, and it may just be that Sins isn't the game for you and your friends. That's fine - it would be a dull world if we all liked the same things - but it doesn't mean that the game itself is bad, just that it's not to your taste.