The above examples appear to be done under some sort of fluorescent lighting, which is known to be a problem for accurate exposures, often causes metering problems. I'd also expect a scene with so much white in it to tend to cause the camera to want to underexpose a lot. So, no surprises there. I think any camera would do something similar, and if those are fluorescent bulbs, that just adds another wild card (FL bulbs "flicker" at a rate of around 60hz, which we don't see with our eyes, but can mess with both the metering and AF system in a camera... FL bulb flickering also can trigger an epileptic seizure in people with that affliction).
The best way to handle FL lighting is to take extra shots, perhaps bracketing exposures.... and check your results before leaving the scene (histogram).
20D, 30D, 40D, 50D and 5D II all use essentially the same 35 zone metering system (I don't know which of the Rebel/xxxD models use it too, but imagine many do). I've seen little difference between the various of these I've used, except for some nuances. For example, 5D/5DII have a much smaller spot than the others (approx. 2.4% of image area, compared to 3.5% on most of the other models).
5DIII, 7D, 60D, T2i/550D, T3i/600D use a different, 63 zone "iFCL" metering system that's improved a little, but also has some nuances of it's own. All 1D use a different metering system, too. Haven't used them enough to comment.
Canon shooters who are using any of the auto exposure modes (Av, Tv, P) often make a practice of setting "ETTR" or "expose to the right". This means simply dialing in +1/3, or sometimes +2/3 Exposure Compensation all the time. It's actually a rather common practice with all Canon and is sort of a bandaid procedure, erring on the side of overexposure rather than underexposure which will cause more noise in images, rather than taking the time to arrive at a really accurate exposure. More about ETTR on this website
(follow links within this article, too).
What metering mode are you using? Unless you are really good at setting exposure by eye, judging exposure compensation if using an AE mode with some EC, Spot Metering and Partial Metering can be difficult to use well. I think they work best with a gray target such as this one (which can be used to set custom white balance at the same time). Some people like and use Center Weighted, which is often good for scenic shots. But Evaluative puts some extra emphasis on the active AF point, so might better compensate for backlighting or extremes that would fool Center Weighted.
Frankly, the way I use my 5DII, usually with stationary subjects and in M or manual mode, I either use a separate, handheld incidence meter such as this one or set the exposure by eye.
An incidence meter measures the light falling onto the subject, rather than what's being reflected off of it. This makes for much more accurate metering. The reading isn't effected by the subject tonality, with incidence metering. With a meter of this type I still might do a little mental "exposure compensation"... slightly overexposing a dark subject to bring out shadow detail or holding back exposure with a light colored subject, to retain detail in highlights. But it's usually in 1/10 stop increments, not in grosser 1/3 or 2/3 or more stop jumps on the scale of the camera, and metering is far more precise.
You can see the difference easily. Take your camera outside in midday, perhaps in a parking lot full of cars of different colors and tonalities (though just about any but the most bland and boring scene will do). Be sure AE Lock is not on and half press the shutter release button while panning across the scene. Watch the meter reading in the viewfinder. It fluctuates wildly, responding to all the different tonalities. Yet, in truth the lighting is even and exposure should be consistent. This is the Achille's Heel of reflective metering. Using an incidence meter properly, you get the same reading time after time after time. But there is no way to effectively build an incidence meter into a camera, so we're stuck with reflective metering.
Setting by eye really isn't a problem, in many common situations. Use the Sunny 16 rule or Cloudy or Shady 11 or Cloudy and Shady 8... or whatever. Take a shot. Check the Histogram. Make some adjustments and take another shot. You can dial it in pretty quickly.
Usually with my 5DII I'm shooting stationary subjects, so M and the above methods of determining exposure are no problem. However, with moving subjects, that are going in and out of sun and shadow or otherwise variable lighting situations, it's different. I'm forced to use one of the auto exposure modes (Av, Tv, P) and rely upon the camera's internal, reflective meter.
For moving subjects, I usually use my 7Ds instead, often set to an AE mode and Evaluative Metering that works pretty well... But I also tend to set those cameras with +1/3 or +2/3 Exposure Compensation as a precaution. More in strongly backlit situations. And it might need to be tweaked + or - a third stop depending upon subject tonality (for example, a white horse would need more + EC, while a black horse will need less, assuming both in the same light... a gray horse or a roan/light chestnut or an apaloosa might need only the "standard" amount of EC).
