I'm sure most of us know that launch games often don't look and feel as good as their counterparts from later in a system's life cycle. Using a classic example, Super Mario Bros. looked better than anything out in 1985 (except for the RDI Halcyon) but Super Mario Bros. 3 looked far better. As much as the NES matured graphically from 1986 to the early 1990s, I nominate a system that had an even bigger gap from launch to maturity.
The Atari 2600.
The specs of the Atari 2600 aren't all that impressive, in fact they aren't a whole lot better than the Fairchild Channel F. But the 2600 had to compete in four generations of systems (I'm not going to call it a 16 bit contemporary, it was pretty much dead by that time). It was around for the first generation, second generation (of which it exemplifies), the "2.5 generation" (ColecoVision, Atari 5200, Vectrex, etc) and the 8-bit generation as a budget alternative. The system survived the video game crash of 1984 and had a lifespan of over 14 years. The system wasn't discontinued until January 1, 1992. By this time, the SNES was out and the Sega CD was out in Japan! This is the same decade that brought us the Dreamcast!
Launch games on the 2600 show this. These 1977 games were a definite step up from Channel F games of the time, but definitely could have been done on the Channel F with some slick programming.
By the time we got to Space Invaders (beginning of 1980) there was evidence of some major maturation of the system. This was an arcade perfect port of a title that launched after the 2600 itself and the system's first "killer app". By 1982, we have Pitfall, a game that graphically looks and plays like an older version of Super Mario Bros. Later, we got games like Tunnel Runner (which had 3D! with scaling monsters), and the post-video game crash games like Solaris. The advancement was such that a game for the 2600 that looked good by 1977 standards looked like a totally different generation by 1983 standards! I credit the system's very flexible hardware, including the lack of a frame buffer. Good developers were able to do things with the 2600.
Any more games that really pushed the 2600? Any other systems that had such a major leap?