It really depends.
There is certainly no secret formula for the perfect album.
Frankly, if an album has all great songs, then there is no question that it's a great album. But, the consistency vs. high-highs/low-lows album debate can go either way.
Take Rush for example:
Now, I prefer Test for Echo over Counterparts (which is already a pretty frowned upon opinion...) I would say T4E has higher highs, what with Driven, Time and Motion, Test for Echo, Resist, etc. But, it also has more frequent lows (although none quite match the shittiness of Double Agent) with Dog Years, Carve Away the Stone, and The Colour of Right.
Counterparts has, for the most part, a pretty solid selection of songs (Leave That Thing Alone, Cut to the Chase, Between Sun & Moon) and a few great songs (Alien Shore, Nobody's Hero), but no songs stand out on the album like they do on T4E for me.
On the other hand, the opposite is true for a band like Symphony X.
The Odyssey has higher highs (The Odyssey) and lower lows (Incantations of the Apprentice) than an album like Twilight in Olympus, which is overall a far more consistent album, but I prefer TiO.
In short, I have no preference, and there is certainly no formula to make a good album other than make every song great.