As far as Osteen being a great preacher: He is neither an exegete, nor is he schooled in the Biblical art, nor is he a theologian, nor is he a minister, nor is he an elder. Other than that, he’s a great man of God.
He’s a marketing guy who took over his father’s televangelist ministry upon his passing. His father had a few peculiar and tenuous beliefs. I’ll say it was decent of him to honor his father and carry it on, but he is entirely too evasive of anything negative, with sin and the consequence of it being chiefly among the matters he evades. There’s a Larry King interview wherein he evades homosexuality being a sin, several others. Osteen may have good intentions or he may just know his audience well enough to keep things positive because that’s what they want to hear. Nothing wrong with that in a motivational speaker, even a nominally Christian one. But, it’s a definite problem in a presumed Pastor leading a church.