Rift is a much different city than Tamriel. Plus the entire empire has gone downhill lately.
Oh gods everything in this sentence.
The Rift is the region in which Riften, the city, is located.
Tamriel is the entire continent containing all of the Privinces, of which Skyrim and Cyrodil are two.
"Riften is a much different city than The Imperial City" would be a bit closer, though less apt. Better to say "Skyrim is a much different land than Cyrodil" but then that's too broad.