See 1-Kings 6:2 note. In Jewish eyes, at the time that the temple was built, it may have been "great," that is to say, it may have exceeded the dimensions of any single separate building existing in Palestine up to the time of its erection.
Great is our God - This may seem inappropriate as addressed to a pagan king. But it appears 2-Chronicles 2:11-12 that Hiram acknowledged Yahweh as the supreme deity, probably identifying Him with his own Melkarth.

And the house which I build is great,.... Not so very large, though that, with all apartments and courts belonging to it, he intended to build, was so; but because magnificent in its structure and decorations:
for great is our God above all gods; and therefore ought to have a temple to exceed all others, as the temple at Jerusalem did.

Great - For though the temple strictly so called, was but small, yet the buildings belonging to it, were large and numerous.