The Last Guardian is the most disappointing exclusive on PS4 since it's by the devs who did Shadow of the Colossus and everyone was expecting another masterpiece out of them. But for the most part the exclusives have been outstanding since Bloodborne released in 2015.
Switch is probably worth buying just for Super Mario Odyssey and Zelda BOTW. It has a respectable library when you count the Wii U ports like Bayonetta 2, Mario Kart 8, and Donkey Kong Tropical Freeze. Yoshi's Crafted World is pretty cool if you want a really casual platformer. Though the other big exclusives are Octopath Traveler and Xenoblade Chronicles 2, which you might be that into if you don't like JRPG.
Astral Chain is the game coming this year on Switch that I'm really interested in since it's developed by Platinum (who is responsible for the combat in NieR Automata).
Since I'm not expecting The Last of Us Part II, Ghost of Tsushima, or Death Stranding this year, Astral Chain is prob second only to Dying Light 2 on my list of most anticipated upcoming releases for 2019. Then my third would probably be the remaster of Link's Awakening coming out on Switch near the end of the year. Mario Maker 2 should be a big hit too, but I doubt it'll be any good on a hacked Switch that can't go online to download levels.