Is the Abrahamic God the only one?

God said He is the only true, living God, and told us why. So why do we need any substitute or 50 million manmade gods to take His place, when He told us He is without sin, perfect, created us and loves us beyond measure, provides, and and possesses everything we need? It's obvious that world religions cannot get one to heaven, because each have their own man-made philosophy on how to get to heaven and have ignored God's perfect Plan of Salvation. Who would know better how to get to heaven, than God, who made the plan? Are men smarter and wiser than God? Hardly. When people don't follow God's plan of salvation, they are calling God a liar, trying to get to heaven their own way and thinking they are smarter than God. That simply won't work. God did not give man that authority. He even warned the children of Israel not to make and worship idols or they would be worshiping the wrong God that could get them to heaven. That same principle applies today.