This year, both Eve Online and Second Life turn six. Yesterday was the big day for Eve Online; Second Life marks the momentous occassion on June 23.
There's a few similarities between the two, apart from their age. Both are persistent single shard, sandbox environments: all inhabitants live in the same instance of the world (or galaxy)and both let inhabitants make their own choices, let them determine their own in world fate. Both environments have a pretty interesting economy: Second Life's stats are freely available here, and CCP even employs an economist to keep track of Eve's money and trade.
Second Life went through some pretty turbulent times, hyped to the sky but also written off, derided and mocked. These six years have been a roller coaster ride! Eve Online's history isn't like that at all, it flew under the radar for quite some time, as it has a reputation of a tough MMO to get a grip on. This, by the way, is improved significantly with the latest Apocrypha expansion.
There's more differences. Second Life counts it's subscribers in the millions, even though the bulk of those are inactive basic (free) accounts; day to day concurrency for Second Life is usually a bit over 70.000 residents. Eve Online's concurrency record stands at 53.000, out of 300.000 active subscriptions. Eve Online does not know free accounts other than the 14 days trial, and according to Massively, CCP doesn't include trial accounts in the 'active accounts' number. This means that 300.000 active accounts really means these are all paid for.
On most evenings, more than 40.000 pilots are active in Eve Online. But, how many of these are individual players isn't clear: it is said that a significant number of players have two or more paid accounts in order to play with several characters at the same time. For instance, the main characters mines asteroids, and an alt transports the mined ore to nearby space stations for selling or processing. In other words, Eve Online's concurrency number isn't necessarily equal to the number of individuals playing. Second Life has somewhat similar issues, mostly with campers and bots (avatars not used by real humans), intended to boost visitor numbers and hence ranking/visibility for shops or clubs in world.
Another difference: CCP celebrates the sixth birthday of it's flagship product with a short blog post and a few gifts for a lottery; Linden Labs throws a big theme party on 20 regions of virtual land. CCP could learn something from Linden Labs in this regard!
In any case, I wish both worlds well. Congratulations, and here's to the next six years!