The comments about "winning under any circumstances" reminds me of a quote from Jackie Stewart: "Show me a gracious loser, and I'll show you a loser".
If we are looking for someone who has raced (and won big) in F1 and excelled in other series look no further than Mario Andretti.
Thing is, every driver that I have mentioned has had the team around them.
Mario's CV is even more impressive than Hill's. F1 WDC, Indy Car Champion, Indy 500 winner, Le Man class winner, Pikes Peak winner, Daytona 500 winner, Sebring 12 hours winner and many more wins in other formulas. GH won the Indy 500 and Le Mans but was never Indy Car champion.
I take issue with the comment about Schumacher lacking composure under pressure, he knew exactly what he was doing when he ran into Hill
Villeneuve etc.
Alonso is known to lack wet weather skills I think otherwise I'd go for him.
I agree with Racecub, Alonso did make the claim back in 2008 that he was the most complete,
Fernando never made that claim. I think the first person to say that was actually Martin Brundle
Alonso came up to me and said, I might not be the fastest but I am the most complete, I would have to agree with that.