Plot was nothing special (it never was PB forte), writing and dialogue however I enjoyed very much. People often make the mistake thinking that only good writing is the PST/KOTOR2 type philosophical stuff (written by MCA) but Risen had good minimalistic writing, the protagonist is a sarcastic asshole (staple of PB games), Bandits are a rough crowd that requires you to carry your own weight and prove yourself, The Order are fanatics that believe the end (the dire situation the whole island is in that people aren't aware of) justify the means, the Harbour City quest conflict between them is excellent (Scordo is one of my favourite PB characters, gives a great speech if you work for the Order) etc. the character are believable, they act and talk the way you expect them which is not an easily accomplished feat in the world of video games, nerds usually fail when writing dialogue for rough convict type characters but PB does it well.
Two villages, one city, all with well designed quests (that usually have multiple approaches), C&C and interesting characters (especially Harbour City, Bandit Camp has some fetch quest crap) .
I found the exploration excellent, PB has a real knack for crafting believable worlds/environments unlike the Bethesda theme parks. Lots of goodies to find (including one of the best swords in the game which you can get early), no level-scaling, a good variety of enemy types (with Ghouls being my absolute favourites, love to fight those guys) great atmosphere (thanks to music, sound effects and visual design) etc.
I even enjoyed the lizard infested dungeons, had some nice (although rudimentary) puzzles as well.
My experience is completely different, combat is miles ahead of Gothic 3 and bug-free. It's also quite fluid with a well designed advancement system (atleast when it comes to melee weapons, you unlock moves and feats instead of +10% damage usual ARPG crap), dodge instead of roll, nice hit-feedback animation, decently intelligent enemies.
Well, for what it's worth, I love IE games (yes, even BG1 and to a lesser extent IWD2) so not in that group.
Different strokes for different folks I guess? I think Roxor's review might be closest to getting into the crux of the matter of why some people really like Risen.