You have probably heard people say that the Garden of Eden was "perfect". Since heaven can also be described as "perfect," you have probably subconsciously equated the Garden with Heaven. But this is a mistake. Although the Garden and Heaven can both be described as perfect, they are perfect in two different senses.
The Garden was perfect in the sense that it was part of God's sovereign plan for history; God created the Garden for a specific purpose, and it fulfilled that purpose perfectly. The Garden can also be described as perfect since it was (at first) untainted by the stain of sin.
Yet in spite of the Garden's many perfections, Heaven will be better. In fact, in comparison to Heaven, the Garden should be undesirable. Why? Because sin was a possibility in the garden! Though the Garden was perfect in many ways, it was lacking in an essential perfection: the assurance that sin would never occur! Heaven is superior to the Garden because in Heaven sin will no longer be a possibility!
Can you imagine the horror of living in a place like the Garden of Eden for all of eternity? A place where you could fall into sin at any moment? A place where even after a hundred or a thousand or a billion years had passed, you would still have no assurance that you would continue in faithfulness to God? Every day would be one more day in which there would be a possibility of falling. Could such a place rightly be called "heaven"? There's a reason the Garden of Eden didn't last forever, because it would not have been heaven.
Don't get caught up in the language that God is planning to one day restore creation to exactly how it was in the beginning. He isn't. Instead, He's planning on doing something better. Much better.
Then the angel showed me the river of the water of life, bright as crystal, flowing from the throne of God and of the Lamb through the middle of the street of the city; also, on either side of the river, the tree of life with its twelve kinds of fruit, yielding its fruit each month. The leaves of the tree were for the healing of the nations. No longer will there be anything accursed, but the throne of God and of the Lamb will be in it, and his servants will worship him. They will see his face, and his name will be on their foreheads. And night will be no more. They will need no light of lamp or sun, for the Lord God will be their light, and they will reign forever and ever. (Revelation 22:1-5)