Most probably the best freeware game ever...

User Rating: 9.5 | Doukutsu Monogatari PC
Cave story (Doukutsu Monogatari) is a freeware 2D platformer release originally in 2004 for the pc and later in 2010 for Wii. It was originally release in japanese, but a free english patch can be found on the internet which translates all dialog into english.

Graphics and sound 9/10
Why am I giving a 9 to a game which is 2D, pixelized and freeware? First of all because graphics don't make a game and second because the portraits you get during dialogs as well as in the ending demo are surprisingly good and really display emotions, much more than some of today perfect looking titles. And the soundtrack is just brilliant, for the era this game is suppose to simulate. Especially the songs towards the end of the game, in the last boss battles and the ending song are really nice.

Story, gameplay and replay value 10/10
The story takes places in the caves of a floating island and features a main hero, a male robot, which cannot remember anything before waking up. The island is inhabited by dog-like creatures called Mimigas, which act all too humanly, including the ability to talk. The main quest of the game is to defeat an evil tyrant, which plans to use the island as a base of operations, and his two henchmen. The story doesn't sound so interesting when put this bluntly. What makes it good are the different endings. A bad one 2/3 through the game where you just escape the island, a good one when you beat the whole game and escape the island together with the few humans trapped there before it falls to earth. And there is even a secret one, an ultimately good one, when you fulfill special requirements and beat a special level as well as an ultimate boss, which saves both, the island from destruction, and saves a female robot which you learn was your teammate before you lost your memories. These endings as well as a healthy dose of dialogs, surprising for a freeware game, make the story a memorable one.
The action is fast and requires a bit of getting used to. The difficulty might seem hard at first, especially during boss fights, but once you get into it it becomes all too easy, with the exception of the secret level which was truly meant to be the hardest one. What makes the action even greater are different weapons you can get and the ways you get them, some are easily achievable, while other require a harder approach. Either way, you trade for weapons using those which you already got, so if you trade your weapon early on for a better one, you will not get the ultimate one which can be traded for the first one only much later on. There is also a minor inventory system with a map, and a few potions gathered on the way, etc.
The replay value is high because of the fun fights, the different endings and loads of secrets founds throughout the game, the biggest one being the secret ending.

The fun fights, which are still fun even when the game is replayed, and the different endings and items you need to collect to obtain them, make for a truly masterpiece of a game, when you consider its category.