There is alot more to choosing a good beginner bike than CCs. For Example a 1200cc Harley Sportster is a decent novice choice. A ZX-6R Ninja is a horrible choice. The Suzuki RG500 is even worse, but the Suzuki GS500 is a great first ride. See the lack of correlation. Its all about the bikes intended purpose.
The EX650R Ninja (the one you are asking about) is a good choice. It was designed as a economical, sporty commuter. It is reasonably comfortable, so you will have one less distraction to contend with. It has a tourquey tractable motor, which is easy to use. It has soft, forgiving, confidence inspiring suspension. It has enough speed and handling to be genuinely entertaining. It is economical. The one negative thing Ive heard is that some have poor break feel, but not all magazines say this, and the one I rode was fine.