At a glance, here are all the major studio releases from Arjen that I am aware of, in chronological order of course:
1994 - Pools Of Sorrow, Waves Of Joy (Arjen Solo)
1995 - The Final Experiment (Ayreon)
1996 - Actual Fantasy (Ayreon)
1998 - Into The Electric Castle (Ayreon)
2000 - Universal Migrator Parts 1 & 2 (Ayreon)
2001 - Fate Of A Dreamer (Ambeon)
2002 - Space Metal (Star One)
2004 - The Human Equation (Ayreon)
2005 - Embrace The Storm (Stream Of Passion)
2008 - 01011001 (Ayreon)
2009 - On This Perfect Day (Guilt Machine)
2010 - Victims Of The Modern Age (Star One)
2012 - Lost In The New Real (Arjen Solo)
2013 - The Theory of Everything (Ayreon)
2015 - The Diary (The Gentle Storm)
2017 - The Source (Ayreon)
2020 - Transitus (Ayreon)
2022 - Revel In Time (Star One)
2023 - Golden Age Of Music (Supersonic Revolution)
About 19 (or 20, depending on if you count Universal Migrator as 1 or 2) albums over the course of 30 years, which isn't bad. He's been about as prolific as any of his contemporaries (Wilson, Morse, Stolt, Tillison) in that time frame, with a lot of various projects and to varying degrees of success. I'd say his peak era would be 2000-2008, though that isn't to say he didn't release spectacular albums before and after that, but from Guilt Machine onwards, I feel like his stuff became hit-or-miss with me personally. I like OTPD a bit but I'd have to be in the mood for it, and I rarely ever go back to The Gentle Storm of the last two Star One albums. And of the three Ayreon albums after 01, I like the The Source a lot, but rarely go back to it - I must be the outlier because I really enjoy TTOE and I've given a fair amount of spins to Transitus over the last few years as well.
I think it'll be time for a new Ayreon album next year or the year after, so hopefully it'll be one that will get the fans back on board!
-Marc.