Year 1998 has become a year of hope for me. After very devastating transition year 1997 there are so many joys and wonderful games at last. Running a bit ahead, there is a 50% increase both in total number of games and in number of listed games resulting in the record number of masterpieces this year.
Let's prolong the chart.
VN per year
Year    Total        
1991    75    

1992    80        
1993    121    

1994    155    

1995    180    

1996    183    

1997    202    

1998    303    

The split is exactly the same featuring 50/50 eroge and galge market and 50% galge market with some additional titles blocked for other than eroge reasons. But look at the numbers, there is a 50% increase in every number compared to 1997. Finally industry got out of slump and gains momentum.

Let's see what year 1998 brought:
The complete shift to Win95-98 platform resulted in dramatic increase in resolution and colors with most works having 256 colors and some reaching 16 bit colors.
With dating SIM dominance substantial shift to pure love stories the number of heroines decreases significantly to just 4-5 and in some cases to just two as in With You ~Mitsumete Itai~ or even one as in DiaboLiQuE without decreasing the volume.
There is a significant number of works where hero is already in relations with the main heroine, but has an option to cheat on her. The starter of that tendency is White Album.
There is a surprising influx of mahjong games, but most of them are blocked as eroge due to having strip element on losing.
Contrary to 1997 there were a lot of major games in 1998. So here is my 1997 masterpieces list. 

• 1. Castle Fantasia ~Seima Taisen~
• 2. Cross Tantei Monogatari ~Motsureta Nanatsu no Labyrinth~
• 3. Double Cast
• 4. Doukoku Soshite...
• 5. EVE: The Lost One
• 6. Exodus Guilty
• 7. First Kiss☆Story
• 8. Hajimari no Kisetsu ~Izakaya Fuyu Monogatari~
• 9. Kisetsu o Dakishimete
• 10. Kuon no Kizuna
• 11. Love Escalator
• 12. luv wave
• 13. One ~Kagayaku Kisetsu e~
• 14. With You ~Mitsumete Itai~

Fourteen. A decent number. What especially pleases the eye is that there are many RPGs and console games. PS1 and Saturn production values were still much bigger than their PC counterparts and that attracted talented story-writers. There are a lot of worthy games in this list, but my heart was stolen by luv wave as soon as I saw it. It's the most serious work in my favorite setting that rose the most of topics for thought. It's a very subjective feeling, of course.