This post is about the original Dragon Ball (not Z, GT, or Super). Here are lists of the Top 10 Strongest fighters on Earth at the beginning of the series (Pilaf Saga) versus the end of the series (Piccolo Junior Saga).
NOTE: These lists are in order from the strongest to the weaker.
I did not include Tien and Chiaotzu on the first list because we do not know how strong they were three or more years before the 22nd World Tournament. Chiaotzu was also too weak to be in any Top 10 Strongest list (I'd rank him below Chappa, who actually is a very strong Human).
Top 10 Strongest on Earth during the Pilaf Saga:
1. Kami (the strongest)
2. Mr. Popo
4. Mercenary Tao
5. Master Roshi
6. Spike the Devil-Man
7. Bandages the Mummy Man
8. General Blue
NOTES: Roshi in the Pilaf and World Tournament Sagas was significantly weaker than he was during the Tien Shinhan and King Piccolo Sagas. I state this because he was equal to Goku at the 21st World Tournament and nearly lost, sustaining damage, but he had done well against Tien in the 22nd World Tournament. Roshi trained before the 22nd World Tournament because he had said Goku surpassed him by training with Korin. This is also why I put Tao above Pilaf Saga Roshi.
See-Through the Invisible Man doesn't even make it in the Top 10 because he was actually very weak. Yamcha had trained for a month before the 21st World Tournament in the wilderness on his own, barely becoming stronger than he had been in the Pilaf Saga. See-Through's only advantage was his invisibility. Without this, he had been easily defeated by Yamcha.
General Blue is the only Superhuman member of the Red Ribbon Army and I won't count androids like Eighter and Metallitron. Colonel Silver and General White are Olympic level athletes at best. Ninja Murasaki is just a normal Human who has a few special abilities and ninja skills.
Top 10 Strongest on Earth during the Piccolo Junior Saga:
1. Goku and Piccolo (on par)
3. Mr. Popo
4. Tien Shinhan
7. Master Roshi
8. Mercenary Tao
9. Master Shen
10. King Chappa