I see both points here and I must say, I fall inside them. That is to say, somewhere in the middle of what Grandpa Kim and Geo are discussing. Alas, I'm not sure of a solution.
On one hand, a multi-player game is like a tournement of several games yet it is unlike it. Of course, due to luck, SE4 is unlike a chess game. It becomes a bit more unlike a chess match in a multi-player game. More luck and more events to "upset" a good player. And, in multi-player games, it's the only place to add the dimension of diplomacy (not found in 1 x 1 games) and this is yet another side of a skilled player. (that AND team coordination).
If we made scoring like a series of 1 x 1 games for each to be rated, I fear there would be no one joining in them. After all, even the best diplomat would be at a disadantage if starting in the corner where a lack of empires to "chat" with would be a bit of an unfair start. (but, that is the "luck" discussion we have had several times...yet, who would want to chance the loss of a 100 points?) In contrast, 5 (for example) different games would "balance" out bad starting positions...assuming a person wasn't unlucky for 5 games in a row
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To make it a personal example, I'd much rather play (and get the rating from) 5 1 x 1 games than take a chance on being Last in a game with 5 rating players. While I recognize I might possible end in first place, I wouldn't want to wager a bad starting position on it.
Without looking back at the formula Geo has suggested, I would propose a "final adjustment" to it that goes like this: after all the points have been computed, we add (and subtract) 1 point for each person beaten (and lost to). A variation of this would be, instead, to add (and subtract) the number of points equal to the number of rated players in the game TIMES the number of players beaten (or lost to). So, in a 5-player game, the loser would get an adjustment of -4 or (considering the second suggestion) -20.
Just some food for thought.