These were the first graphical games that honored the title. Numerous examples of such games have existed over time : Populous, Pong, Tetris, King's Quest, Zaxxon (yeah, it looked 3D, I know), Xenon, Galactix, Raptor, and millions of arcade games and all chess games and board games of all types.
Exceptions to this rule are not uncommon, though. The IBM PC, venerable ancestor of our gigaherz systems of today, was delivered with MS Flight Simulator 1, a squeaky, pixellated version of a flight simulator - but with surprisingly good realism and even a dogfight mode. It was also delivered with an Olympic Games simulator - Decathlon. All ten sports were coded in and playable (at the level of the 4.77Mhz power of the CPU, of course). The rules were simple, obviously, and everything could be done with the arrow keys or a combination indicated on screen before the start of the specific sport event. As soon as the 286 came out, Decathlon was not nearly as playable though. Some sport events were timed and programmed for the 8088, so on a 286 you basically had half the time to do just as many keystrokes - in other words, Mission Impossible.
On the other end of the scale, far from the weak beginnings in the hazy prehistory of gaming, many strong titles of today are still in 2D. Command & Conquer, father of the success of the Real-Time Strategy games, was obviously 2D. So were all the look-alikes C&C Red Alert, of course, but also Dark Reign, Total Annihilation, Starcraft, et al.. I know, some will jump at me saying Total Annihilation is not 2D. But it is. It is presented from a top-down view and the fact that the units have some respect of the terrain does not change the fact that the game has a rather limited notion of altitude outside of ground level. Of course, line-of-sight is correctly calculated and natural obstacles do actually protect against explosions, but despite all this, the game is still in top-down 2D view.
All these games nonetheless brought hours of fun experience to computer users everywhere. It was just as fun to play the game as it was to discover what new trick had been taught to the good old PC. I will develop on this subject in the future - much has to be said about 2D gaming.
But for now, on to games in 3D.