In no particular order
1. Ever 17 (The first thing I'd recommend to anyone, a true classic)
2. Majikoi (Nice VN, nuff said)
3. FSN (too good to not mention it)
4. Aiyoku no Eustia (Somehow it feels compelling and interesting to me, one of the few VN's I play through multiple times) (Oh, and when Yandere translations finish translating this piece in a few months-years)
I've decided to update my top 10 again. The first 4 are all first, because each of them are just so good that I have to rank them equally.
1) Ever17
1) Fate/Stay Night
1) Maji de Watashi ni Koi Shinasai
1) G-Senjou no Maou
5) ef: a fairy tale of the two
6) Cross Channel
7) Sharin no Kuni, Himawari no Shoujo
8) Little Busters!
9) Daibanchou -BIG BANG AGE-
10) Saya no Uta
Honourable mention goes to Deus Machina Demonbane. It's not good enough to get in my top 10, but I have to give it credit for getting me hooked on Lovecraft. Another honourable mention goes to Yume Miru Kusuri, for being both an intriguing story, and the first VN I ever played.
Some that may make it on my list in the future because I haven't finished them (I haven't finished Majikoi cause it's not completely translated, but from what I've played of it, it has definitely earned a spot in my top 10):
-Muv Luv (yet to play Alternative...)
-Kara no Shoujo
-Katahane
-Swan Song
-Steins;Gate
Like the title says, I'd like you to share their top 5 VNs, and honorable mentions that had the potential to make it up there, and why it didn't. I'd rather you not put a reason on why it did make top 5 because usually it's a preference thing, and frankly, I'm not too fond of arguments on preference.
#1 - Fate/Stay Night
#2 - Muv Luv Alternative
#3 - G-Senjou No Maou
#4 - Utawarerumono
#5 - Yume Miru Kusuri - A Drug that Makes you Dream
Honorable Mentions
Edelweiss - It was a great read and I enjoyed every minute of it. However, I felt it was too comical a lot of the time, and I couldn't wrap myself around it. The romance was very strong though. Ran's was comical to no end.
Katawa Shoujo - This easily would've been up there, if there was audio for this!~ I loved the stories, the music especially, and the artwork for this amazing work. If only, if only it had audio it would've been golden.
Wanko to Kurasou - This has that cute element through and through. I every time the protagonist referred to his 'doggies' I felt awkward, he treated them like his daughters which I truly enjoyed. I guess it would be awkward to have sex with your daughters on a bi-season basis though. This VN didn't really have any conflict other than Sylvie, and Risa's route.