I want to buy a new guitar now
And i want a Ibanez! Maybe a rg550 or rg2550z
What ibanez is the best to play on (Not only rg550 or rg2550z)?

I want one that is easy fast to play with!

And btw... Whats the different beetween rosewood and maple? Wich one is best?
try some of the s-series they are definately fun to play

and though people will tell you the difference between rosewood and maple, it basically comes down to preference neither one is better or has distinctly noticable differences when compared to the whole scheme of things between pickups, body wood, amp and effects
well IMO rosewood just looks nicer... and I personally like the RG series and SZ series best, not a fan of the S series. but just try em out yourself, you'll never know otherwise.
Maple fretboards a a little slicker than rosewood fretboards. It's really not that big of a difference in playing in my opinion but there is a difference. I usually pick rosewood for the look.

Neither of the Ibanez' you mentioned is better, just different. Play, then pick.
Out here you've gotta know where your towel is!
+ a few on neither neck type is better, it's all about feel with Ibanez' (or any guitar's) neck surface. Maples tend to be brighter and slicker, maybe for you that means faster. Try them and see what your ears and fingers tell you.