People of all religions, convert to the Islam; or else you will lose in the afterlife

[God – be glorified – explained in the Quran 2: 63 that
Anyone, out of all nations, believes in God, and believes in His apostles and works according to their programs, so that he does not alter the religion of God, and he works righteousness, then in the afterlife, he will have his reward with his Lord:]

{63 Surely, those [Muslims] who believe [in Mohammed],
and those who are Jews,
and Christians,
and Sabaeans

[who died before the coming of Mohammed] –

whosoever believe in God [alone, and believe in His apostles] and the Last Day*, and work righteousness –

shall have their reward [in the afterlife] with their Lord, and there shall no fear [from devils] come upon them [in the Barzakh or afterlife world], neither shall they grieve [for leaving the World following their death.] }
* i.e. who believe in Doomsday.

Those who know Arabic, see the explanation here:

But anyone among all religions who keeps on his beliefs and does not convert to the religion of the Islam --> his righteous work will not be accepted from him, and, in the afterlife, he will be a loser, i.e. will not see Paradise in the afterlife: because he denied the apostle of God: Mohammed the righteous servant of God.