The games might be good, getting to them is not fun.
This is not a review of the games in the collection, but of the collection itself.
Almost every collection nowadays will let you access all the games in it from the start because it's what you payed for, some will add a few extra games that you have to earn the right to play, but the requirements are usually not that harsh.
The GG+ collection will make work for ALL of the games (except the four you get at the beginning). How hard can it be? I'll probably just have to play each game a few times to unlock new ones, right? Nope, you have to earn money in game to buy them.
Oh, so how much money do you need to buy a new game? 30.000 GP? OK, how much do you get per play... ONE HUNDRED!?!
No, no, don't panic yet! Each game has "achievements" that give you a bit more than 100 GP! The problem is, the achievements that give you a decent amount of GP are quite harsh, they are stuff like "Beat 10 levels without dying", "Beat ALL levels without dying".
And unfortunately, these are a one time thing, which means you'll have to get VERY good at EVERY game, even the ones you don't like!
The game also features a mascot for which you can purchase clothes, wigs, etc, etc.... The problem is, while you can customize her, if you actually care about that stuff, she'll only wear the getup while in the main menu, while in a game she'll dress up accordingly to the theme of the game.
Oh, did I forget to mention you CANNOT choose which game or accessory you buy next? The accessories are random and you can only select from one game in each genre while in the shop, so unlocking the game you really want can be more a thing of pure chance than anything else.
While I could recommend the games individually, the process they have chosen to let you access them is the most grueling and frustrating thing ever, if you really want to play these games I'd recommend getting the collection used with the games already unlocked.