Thanks for all this. I stand corrected as regards the charts and your work, I'm not going to challenge it further. A lot of the evidence does really seem to hinge on weekly magazines, so Games-X, Computer Trade Weekly and New Computer Express, so there's limited opportunity for corroboration unless you get into daily local and national news, which online is usually paywalled or institutional access only, as I'm sure you're aware. It's a shame that there's essentially no trace of CTW online. I would still go for the official UK release date being 24 June, personally. The Games-X staff only had access to the game for at least two days by time of publishing Issue 10, so that's in theory 24/25 June at the latest. Monthly magazines I've come across published a week or two beforehand only had unfinished review copies to hand. The NCE chart is admittedly something difficult to overcome as it puts that date into question regardless of what Games-X says. Is it possible that grey imports caused the game to enter the charts before the 24th, or did Gallup only count official stock? P.S. Have you ever thought about becoming an archivist professionally? I mean, did you buy all these magazines one by one and scan them in yourself? That's serious dedication to the craft!
I can only guess as far as grey imports go, but given the close release date between the US and Europe, I'm not sure it would have made a great deal of sense in Sonic's case (if the numbers were even counted). That was really only a practise when there were months, if not years between the official Japanese/American and European releases. One day I'll bother to chart this but my gut instinct is that Sega were quite good at keeping the gap small between US and European launches. It's Nintendo that didn't give a damn - they still had three month gaps as late as the Wii.
I thought 2 was released in the UK in about 1989 and 3 was the one released around August 1991 on the NES?
They only counted official releases as publishers had to send the game packaging into Gallup for a game to get tracked. I didn't scan most of those, I just mirrored them. I did scan any missing issues or pages. I used to buy nearly every magazine that covered Sega from late 1989 until 1993 when the number of magazines getting released became way too many to keep up with. They nearly all got thrown out at some point so I bought most of them again. TBH I find scanning pretty boring, but I do plan to scan some trade papers at some point.
Ah, seems I got a release date mixed up - nevertheless, Japan got SMW a good 9 months before Britain got SMB3, so yeah there was a long period where they were playing the 4th game while we only had the second. As noted, Nintendo gave zero fucks about Europe until fairly recently.
I don't have anything to add to the research, but I just wanted to say that I love topics like this one! It's always fascinating when further research challenges misconceptions we've had for the longest time. I will admit that I'd treated 1991-06-23 as the game's release date as common knowledge over the years, but on looking back I'm pretty got that fact via osmosis from being around others in the community since the end of the '90s, and it appears that they may have gotten this date from Sonic Jam.
Assuming Wikipedia isn't too feisty this year, I added a mention of this temporal discrepancy to the page; hopefully there's more reliable sources unearthed later.