Ripple is centralized.
MtGox is too. Ripple can more easily be made decentralized than MtGox and there are actual plans to do so, compared to MtGox.
Ripple is not open source despite what they say.
The server currently isn't but will be, the principles behind are already better documented than anything on MtGox.
The client is already OpenSource.
Ripple is 100% premined.
XRP are premined, Ripple itself is (just like Bitcoin) more than just a currency. Also, besides a few hundred XRP you can use Ripple without needing them ever again. Currently you get far more than you will ever need in your lifetime for free in this forum.
But bitcoin isn't centralized. The exchange part is always going to be somewhat centralized - doesn't matter if you use otc (IRC operators, OTC orderbook etc), or an exchange. But the network itself is centralized.
The client is open source? The client is not a full client, it is a light node. The server / full node is closed source and is centralized.
Plus, in Ripple you cannot send money or bitcoins, you can only send debt.