android is superior for phones but they're not really competitive in the tablet space. like every couple years a new company springs up with a great one and then you don't hear from them again, this go around it's OnePlus post the price drop. few years ago LG had a couple, as did Huawei, before they got blacklisted in the US anyway. i don't know how Lenovo's are but i expect them to mostly be competing with Samsung so probably not very good.
if you explicitly do not want a walled garden then sure you can find it but it takes a lot of looking for it. reasons for that will include legit reasons like customization, maybe better hardware, specific (and I mean very specific) connectivity, price for value, and of course, piracy. but if you want a good, functional product out the box, consistent updates, and a far better app market (which will include games and compatibility requirements of games), it'll be iPad.
"Maybe it's a tentacle, molesting the planet itself. - Aschen Brodel.