Unless I am mistaken, it seems to me that the Mormon definition of the Terrestrial Kingdom (the second highest kingdom of glory) is essentially identical to mainstream Christianity's definition of Heaven:
- It's a paradise
- You can see Jesus there (just Jesus, he's the only God there)
- You get to see all your deceased loved ones
- You can't become a god
Mormons believe that the Terrestrial Kingdom is where Christians who do not accept the fullness of the Gospel (modern prophets, the Book of Mormon) will go after judgement:
75 These are they who are honorable men of the earth, who were blinded by the craftiness of men.
76 These are they who receive of his glory, but not of his fulness. (D&C 76:75, 76)
If this is true, then that basically means that Mormons believe all the other Christians are going exactly where they believe they are going. And Mormons simply believe in a higher heaven where you can be exalted and become a god, and that not being admitted into this higher heaven would be a type of Hell to them.
Identities of deities and other doctrines aside, after judgement, how does existence in Heaven according to mainstream Christianity, differ from the glory of the Terrestrial Kingdom?