I mean, I think Kimi is fantastic. Only a fool would think he'd be a flop by going back to Ferrari, at the very least he can expect to win more races. But I just think that going forward Hulkenberg is a better long term option because he's got more potential to grow into and I think the guy will just go on improving all the time relentlessly.
Watching Alonso v Kimi would be fun. On paper Alonso ought to come out on top for his utter ruthlessness. But I think there's a chance that he will simply not "get" Kimi and his legendary "meh" attitude. I think he'll be faced with a similar situation to what he had at McLaren where he struggled coming to terms having a rookie who could match him in every area. Heck he even had trouble coping with it all when Trulli had a run of decent form at Renault.
I'd expect Alonso to be the more successful of the two as team-mates but I certainly wouldn't rule Kimi out from playing a few aces of his own, in kind of the way that Button did at McLaren alongside Hamilton and surprised everyone by actually outscoring him across the three seasons they were together,
and if Kimi does prove to be too close for comfort then I can see Alonso hissy fitting his way back to Enstone.