When comparing Gosu vs BlitzMax, the Slant community recommends Gosu for most people. In the question“What are the best 2D game engines?” Gosu is ranked 50th while BlitzMax is ranked 52nd. The most important reason people chose Gosu is:
Gosu is not a game development framework, only a media library that happens to be suited to game development. (Kind of like SDL in the C world.) That means the interface is relatively small.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Lightweight
Gosu is not a game development framework, only a media library that happens to be suited to game development. (Kind of like SDL in the C world.) That means the interface is relatively small.
Pro Mature API, actively maintained and developed
Gosu has been under development since 2001. It is mature and has several toolkits built on top of it to provide additional functionality.

Pro Cross-platform, even mobile, using Ruby
Pro Multi target
You can compile on Windows, Mac and Linux. Nothing to change. There are solutions to compile on the same machine for 2 targets.
Pro Modular
There are many modules to extend the features of the language: you can create PDF (via a Cairo module), or just download/upload files (via LibCurl), playing streaming sound (via BASS) and so on (databases, xml, xls...) User can create their own module (they could be written in plain BlitzMax)
Pro Easy syntax
Based on BASIC syntax. Supports OOP, collections (array, list and map)
Pro Stable language and source code
After many years the language it self is very stable. The packages contains the source code of ALL modules (excluding the source of the compiler).
Pro Easy to start, high productivity
BlitzMax is just ready after the installation. Open the IDE, write your code and just press F5 to see the results. You don't need to install other things to use the language. Of course if you want to change the language itself - or modules - you need to install MinGW or other libs, but guidelines are provided and easy to follow.
Pro Fast compiler
With comparison to the some of the other languages Blitzmax compiles source files fast enough.
Pro Compiles to native code
Good performance thanks to native code on each of the target platforms.
Pro Garbage collected language
The language is garbage collected in two modes: reference counting or using the Boehm-Demers-Weiser conservative garbage collector.
Pro GUI for apps
BlitzMax provides the MaxGUI modules that allow to build GUI desktop applications for Windows, Mac and Linux (FLTK or GTK via a module). You also could create your own 'gadgets'.
Pro Great community support
the forum is plenty of examples and solutions! Community is strong and still working, available for getting an hand
Pro BLIde
BLIde is an integrated development environment for Blitz Max, designed to work very close to the project file management performed by BlitzMax engine.
It’s inspired by the .NET IDE and some other great tools, It’s been designed for hobbyist and professional coders.
Cons
Con Deploying Ruby apps is a mess
Games built with the Ruby to .exe "compiler" do nothing more than extract your source code and Ruby.exe to %TEMP%, then run it. The code is not really compiled at all. The process for wrapping games as Mac apps is a bit nicer, but you'll need a paid Apple Developer subscription to code sign the app, or users will see a warning/error when running your game.
The only way to really compile Ruby is to use RubyMotion, which does not work on Windows and requires a paid subscription on top of the Apple Developer one.
(This Con is not specific to Gosu. Deploying Ruby code has never been fun.)
Con Outdated and abandoned
The author neglected BlitzMax and works on Monkey2.
Con No mobile targets
Only desktop targets available: Windows, MacOS, Linux.
