Hack / Game Hack - isn't it illegal ??

Absolutely NO, game hack is not illegal. Lot of people nowdays confuse the terms. Game hack is just a term used by many people nowdays who do not know what is the meaning of real hack.

Computer hacking is actually a term that is used when one gains access to something that is not his/hers and optains / steals information that does not belong him/her and/or ruins the system.
Game hack does not do any of that, it does not steal anybody's information and changes are not permanent, game hack is a simply memory change (changes made in RAM of computer).

To conclude this shortly, game hack has nothing to do with real term "hack" or "hacker", it is just used by many people nowdays. It is easier to say hack, than say "modification made in real time to get advantage in game" or if you say cheat, that's too general and hard to understand.
Cheat is anything that gives one advantange over another, that includes a proper gaming mouse, keyboard, 27'' or bigger monitor, proper sound setup (7.1 surround or better / 3D sound) ..etc

I (Sethioz) have proper gaming setup, 27'' IPS monitor, RAT 7 adjustable and programmable mouse, Cyborg V7 gaming keyboard and 5.1 / 7.1 surround sound, controller and racing wheel + pedals, which can be considered as cheating versus people who have crappy computer and no proper setup. So cheat is not necesseraly something that changes the game (gives you better weapon or car). Also using game controller i can do what others can't do with mouse and keyboard, so its also "cheating" if you look at it from this point of view.

This is why people simply say "game hack" or "hack" if they see something in game that is not suppouse to be there, but it is a simple modifcation really and it is not illegal in any way.
Such as aimbot, it makes you aim better, it is not a hack that gives you access to restricted information. Just like using huge monitor with proper setup, can be equal to aimbot (i have proven it in some gameplay videos).

If you think game hacking is illegal, you are very wrong and you can stop being a hater. If it would be illegal, then there wouldn't be dedicated game hack creators who have legally registered businesses)