I mean, I suppose one could compare them for that intent, but I don't think that Amtrak is trying to market to the higher-end vacation market to near the same extent that VIA's Canadian does.
But there's still way too many factors unknown to actually make a valid comparison for all but the strongest of railfan that's taking a trip primarily for the train trip, without much regard to what the destination is (and is willing to travel out of their way to get to a preferred starting point.) Most people, even if they are looking at taking the train, have a destination of some sort in mind, or are constrained by their starting point. It's much more feasible for someone in, say, Los Angeles to take the Coast Starlight and fly back from Seattle than to fly up to Winnipeg, take the Canadian, and then fly back from Vancouver. Furthermore, if someone in, say, New York City wants to take a train trip but they also want to visit San Francisco, it will take a lot of effort to convince that person to swing up to Canada to take a train trip just to come back down on an Amtrak segment anyways. Maybe Grand Forks - Seattle vs. WInnipeg - Vancouver? The mileage and time is very different, but the endpoints are about the same and it is a market where someone who wanted to could fairly easily choose between the two (for example, if someone from Grand Forks wanted to get to Vancouver, they could choose to drive to Winnipeg fairly easily.)
VIA's Canadian sleeper class is in a class of its own, probably more comparable to a charter trip that's publicly subsidized rather than an Amtrak sleeper car. It has frequencies that make it rather unuseful to someone who wants to take it with limited, fixed vacation time, and from what I've heard it's held to a higher standard than other VIA trains.
Frankly, I don't see Amtrak really caring if a customer here or there switches from Amtrak to VIA's Canadian. The Canadian is explicitly marketing for the tourist who is choosing a ride specifically for a train ride, at a huge loss to the taxpayer of Canada. I'd rather Amtrak focus their limited funds on sustaining a usable network with adequate food service rather than trimming routes to be unusable to all but a leisure traveler but having the on-board experience for the few that are taking it be 5-star.