Planetarian was alright. It's kinda boring like all visual novels but has a nice setting and hook to it (military guy in the post-apocalypse stumbles upon a planterium with its last functioning robot that doesn't realize the world has ended) and the music is good. It's also pretty short for VN standards at like 5-7 hours.
Clannad is super boring, at least going by the anime. I used to be a KEY fan because I like their depressing fucked up stories and Clannad was the only one I never made it through. I heard after story (the 2nd half of the game) gets good, but it was such a slog.