All consoles have biased reviews, it's not just the Wii and I don't believe the Wii gets it harder than any other console. Every console has it's set of disgruntled idiots just looking to cause a fuss (obviously they succeeded btw).
Firstly, I'm not trying to justify that bad Conduit review, I thought it was crap as well, I'm talking in general from this point onwards.
With the graphics in games, I would say the reason why Wii games get marked down in graphics isn't because they are unjustly compared with HD consoles. The reason is that, the difference between the average Wii game and the graphically best wii game of the day (SMG, MP3, even Zelda, take your pick) is alot bigger than the difference between the average HD game and the best looking HD game of the day on that system.
Sure Killzone 2 and Uncharted may look amazing, but I would not turn my nose down at Resistance (EDIT: Or even Army of Two, a game sitting at 79% on gamerankings), because I think it does an admirable job at looking like it's on the same playing field.
I could say the same thing about the 360 and it's games. I don't think I could say the same about the Wii for most of it's above average to great titles.
The better games on the Wii (NMH and De Blob as examples), do get marked in graphics, but that's because they (and seriously, NO ONE can dispute this) look piss poor graphically compared to the likes of Super Mario Galaxy and Prime 3. NMH's sandbox world is bascally barren. I don't mean to send NMH and De Blob into the firing line here, but you cannot honestly say they look comparable to the Wii's best (Even with colour, De Blob's buildings look bland and the same throughout most of the game, the only character the game has is the blobs themselves and the pesky police things).
So what I'm saying is, I believe that obviously developers tend to focus less on graphics on the Wii, which is fine for most Wii owners (I personally am not sure how I feel about it), but you have to understand that Reviewers have to review the whole game and one component (gameplay) can't make up for a lack of another (graphics).
There are plenty of HD games that get marked down low in the graphics section because they don't compare with the better HD games, it just so happens that it's usually the developers that are just trying to do cheap cash ins. On the other hand, you have the Wii, which has average graphics (for the Wii's capabilities) for both the shovelware and the good games. So obviously Wii's reviews compared to the HD consoles looks weak.
Again, I'm not justifying stupid conduit review guy, I'm just saying that there's a basis (I think) for why Wii games are marked down in graphics by reasonable reviewers and are driven into the ground repeatedly by the Bias ones. But I'd like to say it again, there's people out there that will nitpick games on every console, it's not skewed heavily against the Wii (imo).
This forum alone is enough to tell us that every console has it's detractors. Now if we could just get all of them to write reviews about opposing consoles, may OP wouldn't feel the same way.