I'd recommend getting old sets through bricklink any day though instead of buying new lego from the stores.
While for playmobil I'd say some themes have seen better days, they have some very strong themes at any time still, even now. For lego all the best stuff is long gone, but that might just be my opinion. Sure there is star wars, but thats a license.
Lego peaked in the late eighties, early ninetees.
Great pirates that inspired adventure with its many treasure islands, many beautifull ships, forts of various sizes and even a large trade post.
Plenty of great castles, decorated knights, army builder sets, forestmen and even some medieval civilian sets.
Harbour theme was also strong, with a large and smaller cargo harbour at the same time and the only speedboat harbour ever released.
Space was one great faction after another, always with another focus for each faction. Blacktron where the bad guys with their cool black spacesuits, M-tron had all kinds of ground transports and used lots of magnets, Iceplanet focused on an ice theme, Exploriens focused on finding and examening fosils, UFO had its aliens and robots combined with saucer shaped space ships.
Plenty of city building as well, with buildings other than a police station and firestation. There where also hospitals, a pizzeria, a cafe, various houses, stables, a bank, forrest homes, etc.