At the low Greece had fallen over 90% from the highs in just a couple of years; the Nikkei hasn't fallen 90% despite years of falling CPI. It's hard to imagine what wasn't being discounted at the lows short of a meteor strike.
Whether Greece is still cheap after a 250% rise off the low is a different question. Greece is on my radar but at this point, I'd rather wait for a significant decline to get both the secular and cyclical winds at my back.
Well cheapness in a fundamental sense is always measured by valuation, and never by momentum or overbought/oversold measures, which are more short/medium-term trading factors. I agree that for a trading timeframe of a few days up to say 6 months, timing and overextension are important. But not for trying to own something during a multi-year recovery and then sell it once the economy is back to normal.
About waiting for a decline - this assumes that a decline will occur. Whether or not it is rational to enter at the current price, or wait for a decline, is a classic recurring trading dilemma and can easily be solved with a bit of logical thinking. Consider the following situation:
Market X is trading at $20. You are 99% confident that in 2 year's time it will be trading at $40. However you are aware that it could potentially fall up to 30% between now and 2 years. Do you buy, or wait for a dip?
The answer is very simple - it depends on how likely the dip is to occur. If the chance of a 30% dip from today's price of $20 is 99%, then it would be moronic not to wait for the dip. If the chance of a 30% dip is 1%, then it would be moronic not to buy. Therefore whether to buy or wait for a dip to buy, depends partly on how likely the dip is to occur.
Also, it depends on the size of the gains versus the size of the drawdown. It makes no sense to wait for a 1% drawdown to pass, if you are risking gains of 1000%. Whereas if the drawdown could be 99% and the gains are only 1%, it would be insane to stay in.
Here we have a further trade-off - standing aside risks missing a 100% gain if wrong (and there is no dip). Getting in at the current price risks a 30% drawdown, and missing an 85% extra profit (40/[20-6=14]=185% gain, vs a mere 100% gain if you buy at 20 and sell at 40]. Assuming you can buy the exact low of the dip.
So, let's say the chance of that 30% dip is 50/50. If you wait for a dip and it doesn't occur, you miss a 100% gain. If you wait for a dip and it happens and you buy the low, you make a 185% gain. So your EV is 92.5% (0% gain half the time, 185% gain half the time). If you just buy now, you make a 100% gain both times. So your EV is 100%. Also, in the 'buy now' case your win rate is 100%, vs 50% for the 'buy the dip' case.
Now, if we add some more realistic assumptions, things get even worse for buying the dip. Firstly, you are almost never going to buy the low of the dip. You will usually buy too early, or too late, and sometimes you will miss the trade, or get stopped out on your dip-buying. On a 30% dip you will be doing well if you manage to buy at down 15% on average. So the gains from dip buying are far less. Secondly, even if you buy the exact low, you don't know in advance it's the low. Generally you will still be taking quite large potential risk. If you buy at 30% lower, your realistic risk is still probably another 10 or 20% fall. Both these things significantly lessen the benefits from attempting to dip-buy.
The key point is that for it to be rational to wait to buy the dip, you must be *very confident* that a dip is going to occur before further gains do. And in that case - why aren't you short? If you aren't short, or close to shorting, then you yourself are saying that the odds of a dip are not that great.
And if a dip is unclear or 50/50 - it can never be rational to 'wait to buy the dip', because you are passing up likely big gains (if the bull market continues uninterrupted), for less likely moderate gains (from buying lower IF a dip occurs). That is going against the odds.
Finally, in a bull market what is the chance of a hefty dip? Well, by definition, it is usually *less* than the chance of an even bigger rise. In a bull market, prices tend to go up more than they tend to go down, and the rallies are bigger than the declines.
So, there is only one situation in a bull market where it is rational to be flat and wait for a dip - and that is those situations where the short-term outlook is so bearish or risky that it is, or almost is, a 'trading short'. For example if the Greek government fell in some corruption scandal, or Turkey invaded some disputed tiny coral reef that Greece claimed, or maybe just the Greek market had gone up 50% in 2 months and was highly overbought, then some bearish catalyst appeared. Yes, in that case I would probably get flat and wait for a dip - because the odds of a dip would be so high that it would make no sense to risk staying long, and in fact it would be worth shorting. At all other times, the fact that you are not shorting, means that on your own assessment you think the market is less likely to dip than it is to go higher.
Short version: don't sell out of longs in a bull market, unless you are thinking of going short.