Loads. Off the top of my head:
Mobile first:
Lyne - logic and geometry, really fun
Threes - strategy puzzle game. Don't get the knockoffs, they're not as good.
Mountain Valley - relaxing adventure and geometry puzzler
Buddy and Me - the only running platformer that is genuinely fun to play, it's completely goofy
Ports:
King of Dragon Pass - classic RPG/tribal sim game, works surprisingly well on a touchscreen
Knights of the Old Republic - haven't played it on mobile but it's a classic PC game
Terraria is on mobile, reports are that it works pretty well
The Last Express - a classic adventure game
ScummVM - emulator for all kinds of adventure games, works very well and is worth trying out
GBA and DS emulators - especially good with a phone that has a physical keyboard, but also work well with tablets. I've played Link to the Past and various Pokemon games.
Shadowrun Returns games - well-reviewed RPGs, haven't played but there are ports on the Play Store
Thomas Was Alone - well-reviewed indie game
There's loads of rec lists, just search for them. You will have to pay for games - just like with PC games if it's free or super cheap there's probably a reason - but the prices are a lot lower than PC or console games.
Keep an eye on mobile Humble Bundles and pick them up if any look good. Most mobile games are easy to evaluate and HBs are cheap.
eBooks are also really nice. I prefer eInk readers to phones/tablets because the eInk screens are a lot easier to read on, but ebooks work well on tablets also. PDFs are especially good on tablets. FBReader is my favorite ereader program, CoolReader is also pretty good. I buy lots of books from Baen
http://www.baenebooks.com/ (Sci-fi / Fantasy and DRM-free so I don't need a specific app) and use Calibre
http://calibre-ebook.com/ to manage my ebook library. Project Gutenberg has tons of free public domain books, including classic sci-fi like Andre Norton, classic literary works, etc.
Caveat: Just like with desktops, a crappy tablet won't run games well. If the tablet's MSRP is $170 brace yourself for a bad time. If it was refurbed or on sale, you probably have a better chance for a decent experience.
Can you tone down the flamebait a bit? Just because you don't like a particular form factor doesn't mean it's not great for other people. Try stuff out before judging.