I would agree that alder is quite a bit brighter and little heavier than basswood. But there are differences in basswood between asian basswood and american basswood. The american version is lighter and less dense leading to a warmer overall tone, more balanced while the asian woods tend to be heavier and more dense, transmitting more highs. Of course there will be exceptions to every generality with respect to wood.
Darren at ATD informed me that the RGs use asian basswood while the signature models and J-Custom lines use only american basswood. Have no idea if this is completely accurate or not, but he's spent a lot of time dealing with signature series Ibanez guitars so I figure he's closer to right than I would be on my own.
Alder and ash are typically known as being bright and snappy tonewoods, that's why they are the first choices for Teles and Strats.