Off the top of my head, these are some eroges that are easily available (free or dlsite), at the very least decent, and (for the most part) relatively easy to read, understand and appreciate.
Free:
be alive ~ what is your precious: 3 hours or so, school-setting, utsuge. Although there are multiple endings, one of the routes (the utsuge one) is far more developed and longer than the others, and serves as a true ending.
Novelist wo Ute (Shoot the Novelist): 30 minutes, all-ages, fully voiced. Very high production values for a free work, and a well written, intriguing story - possibly a bit harder to follow than the other games in the list. Unfortunately, only the first chapter has been released so far, and it’s very much a preface to what might end up being quite a large-scale story.
Shimaima: Several hours, partially voiced. It’s along the lines of Alicesoft’s other low budget titles ¬ñ above average production values for the price, emphasis on ero over story. It would be a fairly decent title for 2000-3000 yen, but since it’s free it’s hard to pass up on.
Yugami Kairou: Yandere + Horror, unvoiced, 1 hour ¬ñ like everything else from Pancake, it’s very oddball. It’s pretty much a hit or miss title depending on personal taste.
Doujin: (these are also listed on eng.dlsite)
Hajimete Doushi ~ Bakappuru de Ikou! (Several hours, full voice bar protagonist, single (death by moe) heroine/slice of life pure love, heavyish ero game.) Again, it’s very much a hit or miss title - it’s a very good moege, but on the other hand that’s all there is, as there’s not really any plot at all. Given that the writer (Banya Izumi) is far more renowned for his dark eroges, this game was a real surprise. I’d recommend using a walkthrough, as it’s a bit unnecessarily difficult. Oh, and turn off sound effects for the ero-scenes :lol: - they are truly awful.
Sono Hanabira series: (Around two hours each, schoolgirl yuri, moe, heavyish ero for the length). I’ve played three of them and all have been very similar in structure - single path/heroine with several choices leading to conflict, with a good/game over ending split depending on whether the correct choices have been made earlier in the game. 3 is my favourite as it’s the longest in the series and has the best heroine pairing.
Commercial:
Yami no Koe Special Edition ¬ñ (Several hours for one playthrough, some exceedingly high number of hours to unlock 100% of the scenes) Black Cyc’s first eroge. It hasn’t aged all that well, and it’s decidedly inferior to a lot of their latter works (MinDead Blood onwards). However, it’s worth recommending as an easy to follow title, as all the cast are fully voiced (with one small exception) with no background narrative, so essentially all bar 20 or so lines are voiced, and the focus is on character ‘interactions’ over story. It’s not nearly as ‘dark’ as Black Cyc’s latter works, but it’s still not the sort of thing that would be recommended to everyone.