There's actually one more that I forgot that's really good, and definitely worth reading if you have time! (I'd rank this tied with OSO and spirit migration.) It's less of the linear RPG-esque, but has many of the same elements.
http://www.mangago.me/home/mangalist/90967/?filter=manga
Wow thank you so much for these suggestions! They all seem interesting xD also I wanted to say that slime and remonster were already part of my list, but it's ok ^^ i've also watched log horizon and I enjoyed it as well. Speaking of which, yea, I think it is good to read the manga too eh. I'll definitely check these out! Thank you again for telling me about these ^^
Hey there! I like the RPG-esque feel to manga as well. I clicked through your list, and here are some that I didn't see. (Ones at the top are my most liked!)
I hope you enjoy~
*** http://www.mangago.me/read-manga/spirit_migration_01/ (personal favorite next to OSO)
http://www.mangago.me/read-manga/tensei_shitara_slime_datta_ken/
http://www.mangago.me/read-manga/log_horizon/ (The anime is excellent, but I haven't read the manga yet.)
http://www.mangago.me/read-manga/to_aru_ossan_no_vrmmo_katsudouki/
http://www.mangago.me/read-manga/remonster/