The Muslims do worship the same God, as do the Jews. Howeveer, I think what the Bishops was trying to get across is that Islam does not have the correct view of God…they see our relationship with God as being a master (god) to slave (us) relationship (which explains a lot).
Conversely, Christians see God as the Trinity and we see God the Father as “Abba” (or daddy, father). We also see God as family…we are in a familial relationship with God, He is our Father, we are His children. This is an enormously important difference. It is a far different view to think oneself as being a loved member of a family, rather then being a slave.
So, from a certain point of view the Bishop is correct, because Islam has a very incorrect view of the same God that we worship.