Below are the average review rankings of PC adventure games based on reviews by major sites. I got these 50 games by searching
on this page. You can get a different list by using different search parameters. I searched for Adventure: General (note later changed to Adventure: All), all dates, PC platform, Best Ranking, Minimum Reviews was 10, Average score of Main Sites, 50 results.
EDIT: I did a second search for Adventure-All instead of Adventure-General, which turned up broader results. I'm editing the list below to reflect this.
You can change the parameters. For instance, I could have searched for a Minimum of 5 reviews, but that tends to give mostly just the reviews from the adventure gaming sites, and I wanted to show more of a general ranking, so I asked for a minimum of 10 reviews. You can also search for more than 10 reviews, but this restricts the numbers of games severely, because adventure games don't tend to be reviewed by lots of generalist sites (if that makes sense).
The results are below. You'll notice that a few of these games are not adventures -- so just mentally elimininate them. Despite this flaw, I think the results below do show you which adventure games the generalist sites/reviewers thought were superior.
I'll repost the top 50 from the 2008 Twisty List below that for comparison.
1. Grim Fandango 93.000%
2. The Curse of Monkey Island 89.900%
3. The Longest Journey 88.815%
4. Sam & Max: Season 1 88.063%
5. Sam & Max Episode 205: What's New, Beelzebub? 86.100%
6. Indigo Prophecy 84.898%
7. Sanitarium 84.105%
8. Syberia 83.587%
9. Broken Sword: The Sleeping Dragon 83.289%
10. Escape from Monkey Island PC LucasArts 83.138%
11. Sam & Max Episode 105: Reality 2.0 82.741%
12. Sam & Max Episode 201: Ice Station Santa 82.563%
13. Sam & Max Episode 202: Moai Better Blues 82.300%
14. Outcast 82.017%
15. Syberia II 81.712%
16. Sam & Max Episode 101: Culture Shock 81.500%
17. Myst IV: Revelation 81.278%
18. Sam & Max Episode 203: Night of the Raving Dead 81.231%
19. Sam & Max Episode 104: Abe Lincoln Must Die! 80.889%
20. Sam & Max Episode 106: Bright Side of the Moon 80.571%
21. Gabriel Knight 3: Blood of the Sacred, Blood of the Damned 79.333%
22. Sam & Max Episode 102: Situation: Comedy 79.289%
23. Myst V: End of Ages 79.143%
24. Myst III: Exile 78.890%
25. Evidence: The Last Ritual 78.059%
26. Blade Runner 78.031%
27. Return to Mysterious Island 77.773%
28. Weird Worlds: Return to Infinite Space 77.700%
29. Dreamfall: The Longest Journey 77.058%
30. Uru: Ages Beyond Myst 76.981%
31. Law & Order: Justice is Served 76.793%
32. Penny Arcade Adventures: On the Rain-Slick Precipice of Darkness 76.750%
33. Destination: Treasure Island 76.643%
34. The Egyptian Prophecy 76.455%
35. Runaway: A Road Adventure 76.338%
36. Still Life 75.895%
37. Tony Tough and the Night of Roasted Moths 75.846%
38. Ankh 75.811%
39. AGON: The Mysterious Codex 75.750%
40. Omikron: The Nomad Soul 75.344%
41. Dracula: Origin 75.158%
42. Sherlock Holmes: Nemesis 74.921%
43. Nancy Drew: The White Wolf of Icicle Creek 74.833%
44. Zork Grand Inquisitor 74.818%
45. Secrets of the Ark: A Broken Sword Game 74.774%
46. Echo: Secrets of the Lost Cavern 74.750%
47. A Quiet Weekend in Capri 74.364%
48. Sam & Max Episode 103: The Mole, the Mob and the Meatball 74.267%
49. Voyage: Inspired by Jules Verne 74.235%
50. Bone: The Great Cow Race 74.192%