I thought Gravity was a much better take on space and was a far more entertaining film overall. The acting, the story, the pacing, the visuals and audio (the evolution and rebirth of the main character being shown with unique and fascinating imagery was brilliant), were all superior to Nolan's film, in my opinion. I also like the soundtrack far more in Gravity.
Interstellar had strong acting from it's lead, but poor acting from the supporting cast. It also has a very convoluted and messy plot, a generic save the world "love transcends both time and space" scenario that we've seen in dozens of films, poor pacing (the movie always seemed like it was in a rush when all it really needed to do was slow down), a meaningless cameo by Matt Damon (seriously, why was he even in this movie?), poorly written and sometimes downright cringe worthy dialogue between the actors, I mean... I could go on and on about why this film is a mediocre film and a downright terrible film by the standards set by Nolan himself with previous films like The Prestige and The Dark Knight.
While there are similarities, I contend these are two different types of Sci-Fi; Interstellar being more Sci-Fi/ Fantasy, and I enjoyed both.
And while MM did a fine job of acting, I was also rather taken by the young Murphy and both robotic VA's. And the plot was indeed about 'Love Conquers All', but I rather enjoyed the simplistic way this was presented. And seeing Matt Damon as the villain gave me something to cheer about really; am not a fan generally. And as far as writing, the entire starting scene at the school discussing the history of the space program hit home with me; am tired of revisionist historians interjecting some PC nonsense into the facts.
Liked both films for different reasons.