http://www.mangago.me/read-manga/sengoku_basara_dj_love_devil/
But its a dj which only has two chapters, still it's really good
There's also:
Isekai Maou to Shoukan Shoujo Dorei Majutsu
Tensei Shitara Slime Datta Ken
Doreiku - Boku to 23-nin no Dorei (a game in real life. seinen with sm an lots of psychologigal)
Qishi Huanxiang Ye Manhua
Liar Game (a game in real life. Also has a drama)
Infinity Game
Heart no Kuni No Alice (from an otome game)
Shiro Ari
Battle Royale (another game in real life. Also has a movie)
These I watched the anime, but they have manga:
Btooom!
No Game No Life
Dungeon ni Deai wo Motomeru no wa Machigatteiru Darou ka?
Overlord
Sword Art Online
Amatsuki
Mondaiji-tachi ga Isekai kara Kuru Sou Desu yo?
Deadman Wonderland (a competition in the "real" world but with powers)
Phi Brain - Kami no Puzzle (not really game, but since there's always a puzzle to solve and I think it was a competiton)
Dragon Drive (he's summoned to the world of the game, but it then becomes more normal, and not game-like)
And those are the ones I remember. I really like manga that are game-like or in a game world ヾ(❀╹◡╹)ノ~
almost forgot this one
http://www.mangago.me/read-manga/ore_to_kawazu_san_no_isekai_hourouki/
This one is from my childhood and it's by clamp, it's called magic knight rayearth, the only problem is they are all girl heroes but the guys looks really yummy and it has a really twisted plot that can make you goes wtf. and yea it's an old manga. http://www.mangago.me/read-manga/magic_knight_rayearth/
Battle royale is more of a survival game in an island tho... First japanese live movie in vhs i've watched in the 90s. Only thing about it is it's gory so heads up on that.
Amatsuki is a personal favourite. I idolize the mangaka since day 1. Phenomenal art. Forgot to include that. It's not a game but the boy was transported to a parallel universe. Loveit.
Can any one recommend Game-Like manga sorta like "The Gamer" with magic or levels or reincarnation or summoned to another world... things like that. (preferably with a strong Male lead.)