More variety can at least be found in the upper classes. While Economy Class cabins are very similar in color and seat design, Business and First cabins leave more opportunity for differentiation, and it‘s here that most airlines focus on it.
In fact, Economy Class has seen few improvements in terms of comfort, besides more ergonomically designed seats and maybe inseat video, but Business and First have improved vastly, leaving such a large gap between Business and Economy on longhaul aircraft that some airlines have introduced an enhanced Economy product as well.
Business Class seats are now often more comfortable than older First Class seats and, therefore, First Class now mostly offers flat beds and private cabins. Even this trend is spreading towards Business Class at some carriers, especially those which have abandoned First. Leather seats have become a popular alternative to cloth at many carriers, and the material is also said to last longer