Who is jagad-guru and who is not?

Vasudeva is jagad-guru, as clearly stated here (vasudevam jagad-gurum). One who teaches the instructions of Vasudeva, Bhagavad-gita, is as good as vasudevam jagad-gurum. But when one who does not teach this instruction–as it is–declares himself jagad-guru, he simply cheats the public. Krsna is jagad-guru, and one who teaches the instruction of Krsna as it is, on behalf of Krsna, may be accepted as jagad-guru. One who manufactures his own theories cannot be accepted; he becomes jagad-guru falsely.

Srimad Bhagavatam 8.16.20 purport