Why don't I have a custom title by now?!
The harsh truth, IMO? A programming language alone won't take you very far, anymore, even if you're the absolute BEST living coder for that language alone AND NOTHING MORE beyond that. The IT job market today seems to be oriented towards specific APIs, frameworks and specialization in various business-oriented systems (e.g. CRMs, ERPs, etc.) so logic dictates that the "best" language to learn is the one that "unlocks" most of them.
C/C++ today seem relegated to system/game programming, so unless you truly want to spearhead into that domain, I'd say don't bother: you'll be pwned on the job market by a 1000 LAMP kiddies. Only exception where they might be helpful: as a stepping stone for Objective-C, which cn mean only one thing: OSX and/or iPhone development. But only if you're willing to go down that dark path.
Stuff like FORTRAN and MATLAB seem only useful in academia or relegated to some research positions (e.g. weather models, neural network modeling etc.) and are but a slim minority in the job market, with almost zero job prospects.