Allah wanted to make Adam AS the khalifa of earth. But Iblis wanted to be the khalifa of earth and he was shocked by hearing that, Allah will create a new creation instead of making him the Khalifa.
So my Question is Iblis was already in paradise. Compare to paradise, earth is nothing. Then why did Iblis wanted to be the khalifa of the earth?
This is not correct at all. Iblis's kufr was due to his refusal to obey Allah in prostrating to Adam:
وَإِذْ قُلْنَا لِلْمَلَائِكَةِ اسْجُدُوا لِآدَمَ فَسَجَدُوا إِلَّا إِبْلِيسَ أَبَىٰ وَاسْتَكْبَرَ وَكَانَ مِنَ الْكَافِرِينَ
And (remember) when We said to the angels: "Prostrate yourselves before Adam.'' And they prostrated except Iblis (Shaytan), he refused and was proud and was one of the disbelievers (disobedient to Allah). Surah Al Baqarah [2:34]
The reason why Ibis refused to prostrate is further explained in Surah Saad [38:75 - 78]
٧٤قَالَ يَا إِبْلِيسُ مَا مَنَعَكَ أَنْ تَسْجُدَ لِمَا خَلَقْتُ بِيَدَيَّ ۖ أَسْتَكْبَرْتَ أَمْ كُنْتَ مِنَ الْعَالِينَ٧٥قَالَ أَنَا خَيْرٌ مِنْهُ ۖ خَلَقْتَنِي مِنْ نَارٍ وَخَلَقْتَهُ مِنْ طِينٍ٧٦قَالَ فَاخْرُجْ مِنْهَا فَإِنَّكَ رَجِيمٌ٧٧وَإِنَّ عَلَيْكَ لَعْنَتِي إِلَىٰ يَوْمِ الدِّينِ٧٨
- (Allah) said: "O Iblis! What prevents you from prostrating yourself to one whom I have created with Both My Hands. Are you too proud or are you one of the high exalted'' 76. Iblis said: "I am better than he. You created me from fire, and You created him from clay.'' 77. (Allah) said: "Then get out from here; for verily, you are outcast.'' 78. "And verily, My curse is on you till the Day of Recompense.''
So, there is no evidence at all to say that Iblis wanted to be khalifah of the earth. It was his refusal to obey the command of Allah to prostrate, because of his arrogance in thinking he was better than Adam alaihi as salaam because Adam was created from clay and Iblis from fire.