Considering the variety of different games available to us, let alone the type of games; flash, Internet, computer, video game, it's really hard to be able to say what makes a good game a good game. However, no matter how hard of a question this is, many people are still asking it. I'm sure I could list a few games I love in the console world such as Need For Speed and the ever popular Tom Clancy trilogies, but just because I may like these games, doesn't mean everyone else does! Examples of good games are out there but, they don't really answer the question at hand. All in all I think for everyone, the question; what is a good game? Comes down to a few major attributes. These attributes are included in the following paragraphs, these are of course generalizations and don't count towards or include game titles, there are merely categorical opinions.
The Game Design - In some instances you may hear people talking about the design of the game, and how it does or doesn't "work" with the game. Usually when people are talking about the design they are speaking in specifics of how the game was set up, and the rules of the game or the rules of engagement so to speak. The phrase is also expended to distinguish both the game design embodied in an actual game as well as software documentation that identifies such a design. Other attributes of the gaming design include; narrative, mechanics, visual arts, programming and audio.
Game Play - This includes all player experience during the interaction with gaming systems, particularly formal games. Appropriate utilization is coupled with acknowledgment to "what the player does". Arising alongside game evolution in the 1980s, game play was applied exclusively within the context of video or computer games, though now its popularity has begun to see use in the description of other more traditional game forms. Broadly Speaking, the phrase game play in video game language is used to identify the overall experience of playing the game omitting factors like artwork and sound!
Graphics - Back in the days of the original Nintendo and even flash based games like Asteroids, the graphics were very "blocky" of course most of didn't even realize it at the time until newer consoles like SNES and particularly XBOX and XBOX 360 came out. I think the important of graphics is more steadily sought after nowadays because people want to the best. It's been argued that the differences between XBOX and XBOX 360 are different or aren't different. Just the same, more people have bought XBOX 360 than XBOX, maybe for this reasoning alone.
Game Engine - This is a software system designed for the creation and development of computer and video games. There are many game engines that are contrived to work on video game consoles and desktop operating systems such as Linux, Mac OS X, and Windows. The core functionality typically provided by a game engine includes a rendering engine ("renderer") for 2D or 3D graphics, a physical science engine or collision detection (and collision reaction), sound, scripting, animation, AI, networking, streaming, memory management, threading, and a scene graph. The procedure of game maturation is oftentimes economised by in large part reusing the same game engine to create different games.
Character Creation - Also known as Character generation is the procedure of defining a pretend character for a game. Usually, a character's individual strengths and weaknesses are presented by a set of stats. Games that have a mostly fictional circumstance may include traits such as race and class. Games with a more contemporary or narrower setting may limit customization to physical and personality traits.
Some people play games because of the attributes listed above, and they simply won't play or won't enjoy a game if the graphics are less than perfect or if the characters are annoying or if the game play is buggy, but others, play games simply because it's a way to take a break from the real world, it's a way to get away from the ordinary humdrum of our regular lives, and some of us though sometimes anal about the specifics of a console game, don't use those same criticism when playing something like an online flash based game because we know they aren't made the same way (not really anyway).
Since Asteroids in the 80s, there have been several million different flash based games released, some of these are by big whig companies and others are developed by individuals that simply enjoy making games. These games have come a long way from Asteroids and the like, and now you have all sorts of categories to choose from.
In reality, flash based games can only get better from here on in, but I think that's the same with any type of games or gaming simply because of the technological innovations that keep being created! In the end, it really depends on the user playing the game, as to what makes a good game. You be the judge!