There are sure to be some really great games for it.
This is the thing I am in doubt on. Unless you absolutely must have sony only game like gran turismo or tekken it won't make a difference. I saw the list of game in development for the PS3, only a few were PS3 only and they were the ones you'd expect like Gran Turismo, MSG4, anf Tekken.
Funny story, a friend of mine has bought Sony consoles for the sole purpose of playing Gran Turismo. He played Forza on my 360 and thought it was better. Another friend just got a 360 because he knows he isn't going to afford a PS3. Yet another friend said for $600 he's just going to upgrade his computer instead.
This is the problem with the PS3, the price doesn't justify it. Ok, if you are going to get a Bluray player it will be one of the cheapest. However, you know it's going to suck. Name a console that has a good DVD playback? The PS2 needed a firmware update early on because it couldn't read some DVDs. The 360's DVD playback is not that good. And now the PS3 will have an early Bluray drive which will not be that good as first generation drives usually aren't.
I'm not a fanboy of any system, I go where the games are. I still use my PC because certain genres are better like RTS an FPS. I'm just being realistic and looking through the hype and what has happened in the past.
Then looking at the specs between the 360 and PS3, I think the PS3 is only going to be a little bit better performance. It may have a bigger graphics processor but it has less system memory.
I plan on getting a PS2 when the PS3 comes out, should be able to get one for pretty cheap as people replaced it with the PS3. I was going to get it for Guitar Hero but then a couple weeks ago Activision said Guitar Hero is coming to xbox, so Katamari and God of War might be the only games I have for awhile

But, as you said, it is about marketting. That's one thing Sony does very well. Look at the PS3, they've been copying ideas from the other system lately. I'm not saying the other systems aren't copying ideas, the new 360 camera, someone say EyeToy. But recently Sony said the PS3 is going to have "Entitlements" which sounds jus tlike the current Achievements on the 360. Sony's premium model is going to have chrome accents around the cd dive, just like someone else's premium system.
The reason they are doing this is so when it comes out they can say they have the same stuff and more. Again, good marketting if it works.
I think the number one complaint about the 360 is how "loud" it is. Though it is no louder than the Dreamcast's CD drive churning away. It;s just the cooling fans making the noise and once gameplay starts and there is 5.1 surround going on you don't notice it. I wonder how Sony is going to combat the massive amount of heat their processors are going to put out.
I'm thinking all the reason sony fanboys made fun of the 360 last year (loud, not in stock, etc...) will happen with the PS3 too.
Now, I am also looking forward to the Wii. it sounds cool. However there are problems with that too. i have a feeling there are going to be games that over use the motion sensing. Remember when Cel shading was a big thing and it became overused. I think there will be games that put the motion sensing in for the sake of putting it in even though it doesn't make sense. Of course, as usual, the first party software will probably be rock solid. New Super Mario Bros for the DS is awesome, just completed the game last week.