Moslems believe in one God.
So do Hindus.
 They believe they worship the God of Adam, Noah, Abraham, Moses.
They believe Moses, et al were Moslems who gave the same message to the world that Muhammad did. It's akin to the T'ai-ping leader Hong Xiuquan after reading some Chinese translations of the Bible came to the conclusion that he was the younger brother of Jesus Christ. By your argument, he is still worshipping our God regardless of how wrong his interpretation is.
They believe in daily prayer, fasting, alms giving.
So do many other faiths
All these things are good things.
That is false. Nothing is good unto itself. If you don't do things for God, it's not 'good'.
They are in error that do not worship the Trinity or recognize Jesus as God among other things.
They also believe that Muhammad was the best example of a man, and he had sex with a nine year old.
They believe that killing for their god is good.
Their god is also one of deceit
It is NOT just a matter of the form of God (Triune, etc.) Their version of god is the antithesis of God.
I look on Mohammed much like I look on Arius, Joseph Smith, Charles Russell, or any other person who takes basic Christian belief and twists it to suit their heresy and parts from the Truth.
They're not the same. Arius and the others were from the Christian tradition. Your argument is one that by extension means that anyone, no matter who, no matter where who picks up a Bible and comes to any conclusion is a believer of God.
They are in error and need the Gospel.  That said, I don't believe it correct to say they worship a different God.  They believe wrongly about Him.
There's a better comparison at
http://www.answering-islam.org/lovesus.htmlor
http://www.answering-islam.org/God/character.htmlI don't recall during the Arian controversy any Church Father claimed they worshipped a different God.  Evangelization should start with points of common belief and practice and then pointing out their error.  How do you hope to evangelize them by approaching them with: "You worship Satan! Now let me enlighten you."?  It is much easier to approach them with: "We worship one God, but Christ and Mohammed have different claims and teachings.  Only one of them can be right."
Fr. Deacon Lance
In summary.
Nothing is of itself good.
Other religions also believe in one God, prayer, etc.
Jesus Himself said those are not with me are against me. He also said "Not all who cry Lord! Lord! will be saved"
They are not of the Judeo-Christian tradition; allowing for anyone outside the tradition to come to some kind of wrong conclusion, but say that they're still worshipping the same God (albeit in a false way) is too odd to countenance.
In short the difference is between me saying King John was a king of England and you saying King John was a patch of brown liquid I discovered under my chair last night. Your argument is that we both believe in King John, only one of us is wrong.