I'm not sure Alonso has really had any better options than the decisions he's taken, his only mistake was the complete meltdown with McLaren in 2007. Red Bull were never really an option, which "forced" him in to a long contract with Ferrari who weren't quite good enough to give him a championship 2010-2014, then after that relationship had soured going back to McLaren was his only way into a manufacturer. In hindsight he may also regret losing patience with Ferrari if they go on to win championships in the next couple of years, but in reality I think the complete restructuring of the team was necessary for them to be able to start fresh and move forward.
If he'd just accepted that McLaren weren't going to give him favours to beat Lewis in 2007 his career would have ended up on the same trajectory as Hamilton's and it could even be him in the Mercedes now and he may may have won the championship in 2007/8 as well. Having said that, I suspect the draw of Ferrari would always have been too big for him so he would have ended up there eventually anyway.
Alonso's team moves:
2003: Sauber-Renault - correct decision.
2007: Renault-McLaren - correct decision
2008: McLaren-Renault - forced by circumstances.
2010: Renault-Ferrari - correct decision given options.
2015: Ferrari-McLaren - only option once committing to leaving Ferrari.
For me it's a big chain of decisions that may look like bad judgements at a first glance but he has actually been forced in to because of the crazy year that was 2007. You could say that that's Hamilton's greatest achievement (although he clearly couldn't know the repercussions at the time), as his performances in 2007 prevented a situation where he was either going to be in the same team as Alonso or directly competing for the same seats in other teams as Alonso for possibly the rest of his career.
Edit: oh shit I didn't realise this wasn't the Alonso thread.