Could Garry Kasparov...

Could Kasparov make it back to world no1 and or world champion again now if he really wanted to?

I feel he retired because he wanted to quit when he still felt he was playing great (not sure if he was though) so not becasue he was no longer a contender.

He might return but being the best, it's not possible. His time is up. He knew it and left. 

Honestly I don't know.

There are reasons supporting it and against it.

First, he has retired because IMO he felt he was losing his exceptional strength. Age is a serious factor. A senior player can still win individual games in excellent style, but senior player's actual shape is unstable and this impacts overall results. A senior player can rarely maintain good shape during long tournaments and matches.

Even before his retirement Kasparov avoided matches with Shirov and Ponomariov and rematch with Kramnik. There were monetary reasons and chess politics behind it, but IMHO the main reason was his deteriorating self-confidence.

Kasparov couldn't beat Anand today in a match or achieve better overall tournament results than Carlsen IMO. His play today would resemble Spassky's play in late 80'.

However top OTB chess is in crisis somewhat: 2nd-rate older GM Gelfand demolished younger stars in matches and became challenger. Kasparov could have potential to achieve that too. The reason however isn't their exceptional level of play, both are behind their prime. The true reason is that younger ambitious top GMs except Carlsen are nothing special. I can offer a hypothesis why is that: they prepare exclusively with computers and don't study human play enough.

Let's take a look at Michael Schumacher in Formula 1 after the comeback. He really struggled in 2010, today, he would be in top 5 with some luck. The same is with Kasparov. I guess he would need some tournaments to go through. In 2011 he played eight 5|2 blitzes against Short. 4,5 - 3,5. (VIDEO) I think he would be World Champion again, but nr.1 is less possible.

He avoided Shirov due to lack of confidence, really? If there was anyone he didn't need fearing, it was Shirov.

Classical games: Garry Kasparov beat Alexey Shirov 15 to 0, with 14 draws

Kasparov has nothing else to prove(many GM consider him the greatest), he achived many great thinsg in chess, there is no need for Kasparov to return.

Agreed. So that the battle for number one spot becomes free for all

No the reason is that a friend and I were having a discussion about it. He has got me interested in chess again and also recommended this site. I trust your rudeness is not something I'll come across often here.

For Kasparov returning to chess and finishing in second place in a tournament would be a disappointment. He would want to be sure that he had very good chances of winning, but it just takes too much work to return to that level more than seven years after retirement, also if you are the greatest player ever. Lasker could do similar things, but chess was different in those days.

So I think Kasparov never seriously considers returning to chess, he knows that the result wouldn't be as impressive as his legacy already is. But if he somehow had to return to chess my guess is that he would be top 10 but not top 5, he's after all 50 years old soon. Karpov played continuously and was 48 years old when he left top 10.

I forget where I got it from, but Kasparov himself said that if he returned, he could probably still hold his own in blitz games, but doubted that he'd have the energy to keep up in longer time controls. 

Kasparov seems to still be able to drub lower-rated GMs in blitz games on a regular basis even though he's been retired for 7 years, so the first part of that assertion wouldn't be terribly surprising.

I'm not surprised at the second half either; as fabelhaft pointed out, he's nearly 50. The daily rigors of being at the top isn't easy on the body, especially as you age. It's possible that Kasparov could have maintained a rating high enough to stay relevant, but I doubt he could maintain that kind of energy.