This is just crazy talk. FFVII's world is nowhere near as open as FFVI's or FFV's (especially FFVI's, which allows you to do almost anything in almost any order in the second half of the game) and the soundtrack isn't Uematsu's best either (as he himself admits - he claims his best to be FFIX and I'd consider that roughly tied with FFVI's, which has the opera, Dancing Mad, and the ending theme in its favour). As for changes in mood I don't think any game has ever topped the huge contrast between the World of Balance and the World of Ruin.
I'd probably rank this game fourth in the series after FFVI, FFIX, and FFV (bearing in mind that I haven't played FFXII and a handful of others). Far from a bad game, but definitely not the best in the series.