First of all, you should be aware that AdLib / Soundblaster music works on a different level than MIDI music. A MIDI synthesizer gets high-level instructions like "play an A on a piano" or "play a slightly sharp F# on a violin", and then the MIDI synthesizer does its best to sound like a piano or a violin. That's not how the AdLib or SoundBlaster music synthesizers work.
The music synthesizer in the AdLib and SoundBlaster cards are on a lower level. These synthesizers have fixed general-purpose built-in formulas to generate sounds that imitate some kind of musical instruments. The game can choose from a small set of related formulas and fine-tune them. The sound card has no choice in how it sounds, though. Every OPL2-based sound card calculates the same sound, as it uses the formulas as specified with the adjustment requested by the game. The creative interpretation of the MIDI file is no longer job of the sound card, but of the music playback system included with your game. It's the game that instructs the sound card to sound in a specific way, not the sound card that "chooses" to sound a specific way. This explains why there is no advancement in technology that makes game music sound better on newer cards, with possibly one exception: Some sound cards have the option to enable interesting filters that affect the left and right channel differently, which generates different left and right channel output even on monaureal input, creating a fake stereo impression that sounds more "interesting" than plain mono sound. This kind of filtering is oftentimes called "3D stereo enhancement" or something like that. While the upside of those systems is that this filtering creates more complex sounds from simple boring input sounds, the system has the downside that the random filtering applied to sound that already is carefully mixed and has a nice stereo impression sounds messed up and less defined than it originally was. That's why most people prefer to have this "stereo enhancement" filters disabled, and so AdLib games sound nearly the same on every AdLib compatible soundcard.
There is one advancement, though: Starting with the SoundBlaster Pro 2.0, the OPL2 synthesizer chip was replaced by the OPL3 synthesizer chip. In default configuration, the OPL3 synthesizer chip uses exactly the same formulas as the OPL2 synthesizer chip, so it sounds the same. Games that support the OPL3 chip may configure it to either provide more voices of the same quality as OPL2 voices, or the same amount of voices, but with higher sound complexity. Furthermore, the OPL3 can have each note panned to the extreme left, to the center or the extreme right, while the OPL2 was mono only. To create arbitrary stereo panning, you need to use two OPL3 voices at different volumes: one for the left channel and a second voice for the right channel. In that way of operating the OPL3 chip, you neither get more voices than the OPL2 nor more complex sounds, just arbitrary stereo positions of notes.
So, in the end, it really depends on the game how it uses the extra capabilities of the OPL3, and wether it uses those capabilities at all. For example, Dune 2 is said to make excellent use of the synthesis capabilities provided by the OPL3 chip, while other games might use sound libraries that enable stereo synthesis when selecting OPL3, which you wouldn't notice unless the music files provided with the game actually specify instruments at different stereo positions. To get better (or just different) sound from an OPL2/OPL3 based sound card, you would not swap to a "better soundcard", but instead, you would need to change the software to provide other parameters to the synthesizer chip.
So, there is only one way for a OPL-based sound card to sound "correct", just like there is only one way for a CD player to sound "correct". There are a lot of later SoundBlaster compatible cards that do not sound identical to the OPL2/OPL3. This is because the OPL design is intellectual property of Yamaha, and Yamaha collected royalty fees for every OPL2/OPL3 chip used, so many sound chip vendors started to develop in-house solutions that sound mostly similar to the Yamaha way, but is generated by different formulas that do not infringe Yamaha's intellectual property. As these OPL3 imitations do not sound the way the original OPL3 sounded, this is generally seen as sounding "wrong". Some imitations are regarded as "less wrong", while others are regarded as "terribly wrong", with community oppinions ranking them from least to worst roughly in the order ESS ESFM, Creative CQM, Crystal FM and Analog Devices FM in the AD1816. Your mileage may vary depending on your taste, your expectations and the specific synthesis parameters. The fact that you did not observe any differences between AdLib and your Soundblaster 16 thus is a Good Thing(TM), as it shows that your CT2800 contains an original OPL3 instead of Creative's later CQM synthesizer. It also shows that games often didn't make much use of the extended sound capabilities of the OPL3 synthesizer, which is not a fault of your sound card.
