Jesus spoke about hell far more than He spoke about heaven. The fact that He used extreme examples like plucking our eye out and cutting off our arm, means that we should take His warnings seriously.
He said over and over again that hell is a place of extreme torment, he describes it as an everlasting lake of fire. To be cast into the lake of fire, would be like swimming in red hot lava.
He said that it is forever, where the worm does not die. The reason hell is eternal, is those in hell continue to blaspheme God's name whilst they scream in agony so their sin continues forever as does the punishment.
The Bible does teach that everyone will be rewarded or punished according to his deeds, so we don't all get the same reward or punishment. The important thing is that there won't be an opportunity to repent after death, so our state will be fixed in eternity when we die.
God is glorified by punishing the sinners for all eternity, it shows us how much he hates sin and warns us to repent while we have the opportunity.
Matthew 25:46
And these will go away into eternal punishment, but the righteous into eternal life.
Revelation 20:10
And the devil who had deceived them was thrown into the lake of fire and sulfur where the beast and the false prophet were, and they will be tormented day and night forever and ever.
Matthew 25:41
“Then he will say to those on his left, ‘Depart from me, you cursed, into the eternal fire prepared for the devil and his angels.'"
Revelation 20:15
And if anyone's name was not found written in the book of life, he was thrown into the lake of fire.
Revelation 14:11
And the smoke of their torment goes up forever and ever, and they have no rest, day or night, these worshipers of the beast and its image, and whoever receives the mark of its name.
2 Thessalonians 1:9
They will suffer the punishment of eternal destruction, away from the presence of the Lord and from the glory of his might,
Matthew 13:50
And throw them into the fiery furnace. In that place there will be weeping and gnashing of teeth.
2 Peter 2:4
For if God did not spare angels when they sinned, but cast them into hell and committed them to chains of gloomy darkness to be kept until the judgment;
Jude 1:7
Just as Sodom and Gomorrah and the surrounding cities, which likewise indulged in sexual immorality and pursued unnatural desire, serve as an example by undergoing a punishment of eternal fire.
Revelation 19:20
And the beast was captured, and with it the false prophet who in its presence had done the signs by which he deceived those who had received the mark of the beast and those who worshiped its image. These two were thrown alive into the lake of fire that burns with sulfur.
Mark 9:43
And if your hand causes you to sin, cut it off. It is better for you to enter life crippled than with two hands to go to hell, to the unquenchable fire.
Matthew 5:29
If your right eye causes you to sin, tear it out and throw it away. For it is better that you lose one of your members than that your whole body be thrown into hell.